All living and sentient things are formed out of insentient atoms.
He established the existence of molecules and atoms as we have defined above, and stated that the number of atoms in the molecule is generally 2, but may be 4, 8, &c. We cannot tell whether his choice of the powers of 2 is accident or design.
He regarded the chemical properties of a substance as due to (1) the chemical atoms composing it, and (2) the structure, and he asserted that while different compounds might have the same components (isomerism), yet only one compound could have a particular structure.
Atoms attract each other and atoms repel one another.
The molecule of every compound must obviously contain at least two atoms, and generally the molecules of the elements are also polyatomic, the elements with monatomic molecules (at moderate temperatures) being mercury and the gases of the argon group. The laws of chemical combination are as follows: I.
Thus, the symbols 14 2 and P4 indicate that the molecules of hydrogen and phosphorus respectively contain 2 and 4 atoms. Since, according to the molecular theory, in all cases of chemical change the action is between molecules, such symbols as these ought always to be employed.
The Daltonian would say that each of these weights represents a certain group of atoms, and that these groups can replace, or combine with, each other, to form new molecules.
If a compound contains two atoms it is termed a binary compound, if three a ternary, if four a quaternary, and so on.
the relative weights of atoms. He took hydrogen, the lightest substance known, to be the standard.
Pascal and other members of Port Royal openly expressed their doubts about the place allowed to God in the system; the adherents of Gassendi met it by resuscitating atoms; and the Aristotelians maintained their substantial forms as of old; the Jesuits argued against the arguments for the being of God, and against the theory of innate ideas; whilst Pierre Daniel Huet (1630-1721), bishop of Avranches, once a Cartesian himself, made a vigorous onslaught on the contempt in which his former comrades held literature and history, and enlarged on the vanity of all human aspirations after rational truth.
The atoms have already learned this law, and are pregnant by it.
There is no such thing really as a vacuum, any more than there are atoms or ultimate indivisible particles.
Hence the gaseous atoms of hydrogen and oxygen could not have parts.
The force which brings the atoms together in the forms of objects is inherent in the elements, and all their motions are necessary.
The force which brings the atoms together in the forms of objects is inherent in the elements, and all their motions are necessary.
The atomist has an easy answer; he says that the new body is made up by the juxtaposition of the atoms of iodine and mercury, which still exist in the red powder.
Following Newton, he believed a gas to be made up of particles or atoms, From Dalton's Hydrogen Gas.
In both these doctrines of a priori science Descartes has not been subverted, but, if anything, corroborated by the results of experimental physics; for the so-called atoms of chemical theory already presuppose, from the Cartesian point of view, certain aggregations of the primitive particles of matter.
These atoms, which are the seeds of all things, are, however, not eternal but created by God.
The gradual accumulation of data referring to organic compounds brought in its train a revival of the discussion of atoms and molecules.
In both these doctrines of a priori science Descartes has not been subverted, but, if anything, corroborated by the results of experimental physics; for the so-called atoms of chemical theory already presuppose, from the Cartesian point of view, certain aggregations of the primitive particles of matter.
It may have some limit in theory, because there is an optimal arrangement of atoms in the universe; but for practical purposes, it has no limit.
It is evident that this is practicable if the number and kind of atoms contained in the molecule of a compound can be determined.
It is now agreed that the molecule of water contains two atoms of hydrogen and one of oxygen, so that the atomic weight of oxygen becomes 16, and similarly that the molecule of ammonia contains three atoms of hydrogen and one of nitrogen, and that consequently the atomic weight of nitrogen is 14.
PYRIMIDINES, METADIAZINES or Miazines, in organic chemistry, a series of heterocyclic compounds containing a ring complex, composed of four carbon atoms and two nitrogen atoms, the nitrogen atoms being in the meta-position.
345), that only compounds containing two carbon atoms yielded fulminates, points to (Hcno) 2; on the other hand, Wohler (loc. cit.
Their fundamental conception is that of Democritus; they seek to account for the formation of the cosmos, with its order and regularity, by setting out with the idea of an original (vertical) motion of the atoms, which somehow or other results in movements towards and from one another.
" The subsidiary rays of medals and inscriptions, of geography and chronology, were thrown on their proper objects; and I applied the collections of Tillemont, whose inimitable accuracy almost assumes the character of genius, to fix and arrange within my reach the loose and scattered atoms of historical information."
He denied that gaseous atoms could have parts, although compound gases could.
He defined structure " as the manner of the mutual linking of the atoms in the molecule," but denied that any such structure could give information as to the orientation of the atoms in space.
According to this view, it is necessary to assume that, in all unsaturated compounds, two, or some even number of affinities are disengaged; and also that all elements which combine with an even number of monad atoms cannot combine with an odd number, and vice versa, - in other words, that the number of units of affinity active in the case of any given element must be always either an even or an odd number, and that it cannot be at one time an even and at another an odd number.
that the sum of the units of affinity of all the atoms in a compound is an even number.
Groups of two or more atoms like SO 2 and OH, which are capable of playing the part of elementary atoms (that is to say, which can be transferred from compound to compound), are termed compound radicals, the elementary atoms being simple radicals.
It is often convenient to regard compounds as formed upon certain types; alcohol, for example, may be said to be a compound formed upon the water type, that is to say, a compound formed from water by displacing one of the atoms of hydrogen by the group of elements C 2 H 5, thus - H C2H5 O H O H Water Alcohol.
Changes of the first and second kind, according to our views of the constitution of molecules, are probably of very rare occurrence; in fact, chemical action appears almost always to involve the occurrence of both these kinds of change, for, as already pointed out, we must assume that the molecules of hydrogen, oxygen and several other elements are diatomic, or that they consist of two atoms. Indeed, it appears probable that with few exceptions the elements are all compounds of similar atoms united together by one or more units of affinity, according to their valencies.
We may suppose that in the formation of gaseous hydrochloric acid from gaseous chlorine and hydrogen, according to the equation H2 +C1 2 = HCI+HC1, a certain amount of energy is expended in separating the atoms of hydrogen in the hydrogen molecule, and the atoms of chlorine in the chlorine molecule, from each other; but that heat is developed by the combination of the hydrogen atoms with the chlorine atoms, and that, as more energy is developed by the union of the atoms of hydrogen and chlorine than is expended in separating the hydrogen atoms from each other and the chlorine atoms from one another, the result of the action of the two elements upon each other is the development of heat, - the amount finally developed in the reaction being the difference between that absorbed in decomposing the elementary molecules and that developed by the combination of the atoms of chlorine and hydrogen.
Lastly, in the production of gaseous hydriodic acid from hydrogen and solid iodine H2 - 1 - 12=HI+HI, so much energy is expended in the decomposition of the hydrogen and iodine molecules and in the conversion of the iodine into the gaseous condition, that the heat which it may be supposed is developed by the combination of the hydrogen and iodine atoms is insufficient to balance the expenditure, and the final result is therefore negative; hence it is necessary in forming hydriodic acid from its elements to apply heat continuously.
His unitary conceptions may be summarized: every chemical compound forms a complete whole, and cannot therefore consist of two parts; and its chemical character depends primarily upon the arrangement and number of the atoms, and, in a lesser degree, upon their chemical nature.
von Hofmann continued the investigation, and established their recognition as ammonia in which one or more hydrogen atoms had been replaced by hydrocarbon radicals, thus formulating the " ammonia type."
Williamson showed how alcohol and ether were to be regarded as derived from water by substituting one or both hydrogen atoms by the ethyl group; he derived acids and the acid anhydrides from the same type; and from a comparison of many inorganic and the simple organic compounds he concluded that this notion of a " water-type " clarified, in no small measure, the conception of the structure of compounds.
The " structure theory " (or the mode of linking of the atoms) of carbon compounds, founded by Butlerow, Kekule and Couper and, at a later date, marvellously enhanced by the doctrine of stereo-isomerism, due to J.
By its aid the molecule is represented as a collection of atoms connected together by valencies in such a manner that the part played by each atom is represented;.
This description, although not absolutely comprehensive, serves as a convenient starting-point for a preliminary classification, since a great number of substances, including the most important, are directly referable to hydrocarbons, being formed by replacing one or more hydrogen atoms by other atoms or groups.
There also exists an extensive class of compounds termed the " heterocyclic series " - these compounds are derived from ring systems containing atoms other than carbon; this class is more generally allied to the aromatic series than to the aliphatic.
Gomberg's triphenyl-methyl play no part in what follows), it is readily seen that the simplest hydrocarbon has the formula CH 4, named methane, in which the hydrogen atoms are of equal value, and which may be pictured as placed at the vertices of a tetrahedron, the carbon atom occupying the centre.
The equivalence of the four hydrogen atoms of methane rested on indirect evidence, e.g.
Let us now consider hydrocarbons containing 2 atoms of carbon.
Three such compounds are possible according to the number of valencies acting directly between the carbon atoms. Thus, if they are connected by one valency, and the remaining valencies saturated by hydrogen, we obtain the compound H 3 C CH 3, ethane.
If the carbon atoms are connected by two valencies, we obtain a compound H2C:CH2, ethylene; if by three valencies, HC: CH, acetylene.
In methane and ethane the hydrogen atoms are of equal value, and no matter which one may be substituted by another element or group the same compound will result.
(methylene) groups and the molecule consists of a single chain; such hydrocarbons are referred to as being normal; (2) has a branch and contains the group; CH (methine) in which the free valencies are attached to carbon atoms; such hydrocarbons are termed secondary or iso-; (3) is characterized by a carbon atom linked directly to four other carbon atoms; such hydrocarbons are known as tertiary.
Considering derivatives primarily concerned with transformations of the hydroxyl group, we may regard our typical acid as a fusion of a radical R CO - (named acetyl, propionyl, butyl, &c., generally according to the name of the hydrocarbon containing the same number of carbon atoms) and a hydroxyl group. By replacing the hydroxyl group by a halogen, acid-haloids result; by the elimination of the elements of water between two molecules, acid-anhydrides, which may be oxidized to acid-peroxides; by replacing the hydroxyl group by the group. SH, thio-acids; by replacing it by the amino group, acid-amides (q.v.); by replacing it by the group - NH NH2, acid-hydrazides.
In classifying closed chain compounds, the first step consists in dividing them into: (1) carbocyclic, in which the ring is composed solely of carbon atoms - these are also known as homocyclic or isocyclic on account of the identity of the members of the ring - and (2) heterocyclic, in which different elements go to make up the ring.
It was long supposed that the simplest ring obtainable contained six atoms of carbon, and the discovery of trimethylene in 1882 by August Freund by the action of sodium on trimethylene bromide, Br(CH 2) 3 Br, came somewhat as a surprise, especially in view of its behaviour with bromine and hydrogen bromide.
The separation of carbon atoms united by single affinities in this manner at the time the observation was made was altogether without precedent.
The values in other cases are calculable from the formula RI 09° 28' - a), where a is the internal angle of the regular polygon contained by sides equal in number to the number of the carbon atoms composing the ring.
As an illustration it may be pointed out that in the case of the two known types of lactones - the y-lactones, which contain four carbon atoms and one oxygen atom in the ring, are more readily formed and more stable (less readily hydrolysed) than the S-lactones, which contain one oxygen and five carbon atoms in the ring.
That the number of atoms which can be associated in a ring by single affinities is limited there can be no doubt, but there is not yet sufficient evidence to show where the limit must be placed.
The ringed structure of benzene, C 6 H 61 was first suggested in 1865 by August Kekule, who represented the molecule by six CH groups placed at the six angles of a regular hexagon, the sides of which denoted the valencies saturated by adjacent carbon atoms, the fourth valencies of each carbon atom being represented as saturated along alternate sides.
From these nuclei an immense number of derivatives may be obtained, for the hydrogen atoms may be substituted by any of the radicals discussed in the preceding section on the classification of organic compounds.
It has already been stated that benzene derivatives may be regarded as formed by the replacement of hydrogen atoms by other elements or radicals in exactly the same manner as in the aliphatic series.
Although Kekule founded his famous benzene formula in 1865 on the assumptions that the six hydrogen atoms in benzene are equivalent and that the molecule is symmetrical, i.e.
These results may be graphically represented as follows: numbering the hydrogen atoms in cyclical order from i to 6, then the first thesis demands that whichever atom is substituted the same compound results, while the second thesis points out that the pairs 2 and 6, and 3 and 5 are symmetrical with respect to 1, or in other words, the di-substitution derivatives 1.2 and 1.6, and also 1.3 and 1.5 are identical.
The proof is divided into two parts: (1) that four hydrogen atoms are equal, and (2) that two pairs of hydrogen atoms are symmetrical with reference to a specified hydrogen atom.
These three acids yield on heating phenol, identical with the substance started with, and since in the three oxybenzoic acids the hydroxyl groups must occupy positions other than I, it follows that four hydrogen atoms are equal in value.
Petermann (Ann., 1869, 149, p. 129) provided the proof of the equivalence of the atoms 2 and 6 with respect to 1.
Therefore there must be another pair of hydrogen atoms, other than 2 and 6, which are symmetrical with respect to 1.
The trimolecular polymerization of numerous acetylene compounds-substances containing two trebly linked carbon atoms, -C: C -, to form derivatives of benzene is of considerable interest.
Generally rupture occurs at more than one point; and rarely are the six carbon atoms of the complex regained as an open chain.
Zincke; and his researches have led to the discovery of many chlorinated oxidation products which admit of decomposition into cyclic compounds containing fewer carbon atoms than characterize the benzene ring, and in turn yielding openchain or aliphatic compounds.
In general, the rupture occurs between a keto group (CO) and a keto-chloride group (CC1 2), into which two adjacent carbon atoms of the ring are converted by the oxidizing and substituting action of chlorine.
Ladenburg (Ber., 2, p. 140) devised his prism formula (IV), the six carbon atoms being placed at the six corners of a right equilateral triangular prism, with its plane projections (V, VI).
CH CH HC, N CH HC CH HC HC HC Hcch Hc Ch Ch Kekule t i Dewar Ladenburg One of the earliest and strongest objections urged against Kekule's formula was that it demanded two isomeric ortho-di-substitution derivatives; for if we number the carbon atoms in cyclical order from i to 6, then the derivatives 1.2 and 1.6 should be different.'
The former pointed out that the supposed isomerism was not due to an arrangement of atoms, but to the disposition of a valency, and therefore it was doubtful whether such a subtle condition could exert any influence on the properties of the substance.
By projecting Ladenburg's prism on a plane and numbering the atoms so as to correspond with Kekule's form, viz.
that 1.2 and 1.6 should be ortho-positions, 1.3 and 1.5 meta-, and 1.4 para-, and following out the transformation on the Ladenburg formula, then an ortho-dioxyterephthalic acid (IV) should result, a fact denied by experience, and inexplicable unless we assume a wandering of atoms. Kekule's formula (III), on the other hand, is in full agreement (Baeyer).
The transformation is not one of the oxidation of a hexamethylene compound to a benzenoid compound, for only two hydrogen atoms are removed.
He numbers the carbon atoms placed at the corners of a hexagon from i to 6, and each side in the same order, so that the carbon atoms i and 2 are connected by the side 1, atoms 2 and 3 by the side 2, and so on.
A doubly linked pair of atoms is denoted by the sign A with the index corresponding to the side; if there are two pairs of double links, then indices corresponding to both sides are employed.
From these results Baeyer concluded that Claus' formula with three para-linkings cannot possibly be correct, for the Q2.5 dihydroterephthalic acid undoubtedly has two ethylene linkages, since it readily takes up two or four atoms of bromine, and is oxidized in warm aqueous solution by alkaline potassium permanganate.
When applied to benzene, a twofold conjugated system is suggested in which the partial valencies of adjacent atoms neutralize, with the formation of a potential double link.
It is well known that singly, doubly and trebly linked carbon atoms affect the physical properties of substances, such as the refractive index, specific volume, and the heat of combustion; and by determining these constants for many substances, fairly definite values can be assigned to these groupings.
These bands are due to molecular oscillations; Hartley suggests the carbon atoms to be rotating and forming alternately single and double linkages, the formation of three double links giving three bands, and of three single links another three; Baly and Collie, on the other hand, suggest the making and breaking of links between adjacent atoms, pointing out that there are seven combinations of one, two and three pairs of carbon atoms in the benzene molecule.
that the hydrogen atoms must all lie in one plane.
The proof of this statement rests on the fact that if the hydrogen atoms were not co-planar, then substitution derivatives (the substituting groups not containing asymmetric carbon atoms) should exist in enantiomorphic forms, differing in crystal form and in their action on polarized light; such optical antipodes have, however, not yet been separated.
Ladenburg's prism formula would give two enantiomorphic ortho-di-substitution derivatives; while forms in which the hydrogen atoms are placed at the corners of a regular octahedron would yield enantiomorphic tri-substitution derivatives.
The octahedral formula discussed by Julius Thomsen (Ber., 1886, 19, p. 2 944) consists of the six carbon atoms placed at the corners of a regular octahedron, and connected together by the full lines as shown in (I); a plane projection gives a hexagon with diagonals (II).
Marsh also devised a form closely resembling that of Thomsen, inasmuch as the carbon atoms occupied the angles of a regular octahedron, and the diagonal linkages differed in nature from the peripheral, but differeng from Thomsen's since rupture of the diagonal and not peripheral bonds accompanied the reduction to hexamethylene.
Two parallel triangular faces are removed from a cardboard model of a regular octahedron, and on the remaining six faces tetrahedra are then placed; the hydrogen atoms are at the free angles.
Zeit., 1905, 29, p. 30), assumed the six carbon atoms to occupy six of the corners of a cube, each carbon atom being linked to a hydrogen atom and by single bonds to two neighbouring carbon atoms, the remaining valencies being directed to the unoccupied corners of the cube, three to each, where they are supposed to satisfy each other.
Restricting ourselves to compounds resulting from the fusion of benzene rings, we have first to consider naphthalene, C10H8, which consists of two benzene rings having a pair of carbon atoms in common.
If a-naphthylamine and a-naphthol be reduced, the hydrogen atoms attach themselves to the non-substituted half of the molecule, and the compounds so obtained resemble aminodiethylbenzene, C 6 H 3 NH 2 (C 2 H 5) 21 and oxydiethylbenzene, C 6 H 3.
(7) (2) In the first symbol it is assumed that one of the affinities of each of the two central carbon atoms common to the two rings acts into both rings, an assumption involving a somewhat wide departure from all ordinary views as to the manner in which affinity acts.
The centric formula proposed by Bamberger represents naphthalene as formed by the fusion of two benzene rings, this indicates that it is a monocyclic composed of ten atoms of carbon.
Similarly, two or more methine groups may be replaced by the same number of nitrogen atoms with the formation of rings of considerable stability.
Most of the simple ring systems which contain two adjacent carbon atoms may suffer fusion with any other ring (also containing two adjacent carbon atoms) with the production of nuclei of greater complexity.
Heterocyclic rings may be systematically surveyed from two aspects: (I) by arranging the rings with similar hetero-atoms according to the increasing number of carbon atoms, the so-called " homologous series "; or (2) by first dividing the ring systems according to the number of members constituting the ring, and then classifying these groups according to the nature of the hetero-atoms, the so-called " isologous series."
The transition between the two classes as differentiated above may be illustrated by the following cyclic compounds, each of which contains a ring composed of four carbon atoms and one oxygen atom: CH CH/ CH CH/ CH CO I CH CO' CH =CH c Tetramethylene But yrolactone.
The formulae of these substances are: By substituting one or more CH groups in these compounds by nitrogen atoms, ring-systems, collectively known as azoles, result.
Obviously, isomeric ring-systems are possible, since the carbon atoms in the original rings are not all of equal value.
Thus furfurane yields the following rings by the introduction of one and two nitrogen atoms: CH=N N=CH..
Thiophene also gives rise to triazsulphole, three nitrogen atoms being introduced.
Six-membered ring systems can be referred back, in a manner similar to the above, to pyrone, penthiophene and pyridine, the substances containing a ring of five carbon atoms, and an oxygen, sulphur and nitrogen atom respectively.
From the pyrone ring the following series of compounds are derived (for brevity, the hydrogen atoms are not printed): Penthiophene gives, by a similar introduction of nitrogen atoms, penthiazoline, corresponding to meta-oxazine, and para-thiazine, CH 2 CH 2o CH CO „ .„0 C ?
The skeletons of these types are (the carbon atoms are omitted for brevity): We have previously referred to the condensation of heterocyclic ring systems containing two vicinal carbon atoms with benzene, naphthalene and other nuclei.
One or two benzene nuclei may suffer condensation with the furfurane, thiophene and pyrrol rings, the common carbon atoms being vicinal to the hetero-atom.
Typical formulae are (R denoting 0, S or NH): Isomers are possible, for the condensation may be effected on the two carbon atoms symmetrically placed to the hetero-atom; these isomers, however, are more of the nature of internal anhydrides.
the manner in which the atoms are linked together; and (3) the configuration of the molecule, i.e.
the arrangement of the atoms in space.
Similarly, an increase of volume is associated with doubly and trebly linked carbon atoms.
If, however, an amount of energy a is taken up in separating atoms, the ratio is expressible as C p /C„= (5+a)/(3-Fa), which is obviously smaller than 5/3, and decreases with increasing values of a.
Regnault confirmed Neumann's observations, and showed that the molecular heat depended on the number of atoms present, equiatomic compounds having the same molecular heat.
the amount which is equivalent to one part of hydrogen; and (2) a factor which denotes the number of atoms of hydrogen which combines with or is equivalent to one atom of the particular element.
This is shown in the case of the chloracetic acids: According to van 't Hoff the substitution of chlorine atoms into a methyl group occasions the following increments: The introduction of chlorine, however, may involve a fall in the boiling-point, as is recorded by Henry in the case of the chlorinated acetonitriles: NC CH 3.
An ethylenic or double carbon union in the aliphatic hydrocarbons has, apparently, the same effect on the boiling-point as two hydrogen atoms, since the compounds C 0 H 2 „ +2 and CoH2n boil at about the same temperature.
Now in both cases one gramme-molecule of oxygen is decomposed, and the two oxygen atoms thus formed are combined with two carbon valencies.
Thus oxygen varies according as whether it is linked to hydrogen (hydroxylic oxygen), to two atoms of carbon (ether oxygen), or to one carbon atom (carbonyl oxygen); similarly, carbon varies according as whether it is singly, doubly, or trebly bound to carbon atoms.
C. C. Baly regards colour as due to " isorropesis " or an oscillation between the residual affinities of adjacent atoms composing the molecule.
This tautomerism may be of a twofold nature :-(I) it may involve the mere oscillation of linkages, as in acridine; or (2) it may involve the oscillation of atoms, as in fluorescein.
molecular weight, is constant for isomers, and that two atoms of hydrogen were equal to one of carbon, three to one of oxygen, and seven to one of chlorine; but these ratios were by no means constant, and afforded practically no criteria as to the molecular weight of any substance.
- On the theory that crystal form and structure are the result of the equilibrium between the atoms and molecules composing the crystals, it is probable, a priori, that the same substance may possess different equilibrium configurations of sufficient stability, under favourable conditions, to form different crystal structures.
We may therefore regard the nitrogen atoms as occupying the centres of a cubic space lattice composed of iodine atoms, between which the hydrogen atoms are distributed on the tetrahedron face normals.
Coplanar substitution in four hydrogen atoms would involve the pushing apart of the iodine atoms in four horizontal directions.
If the crystal structure be regarded as composed of 0 three interpenetrating point systems, one consisting of sulphur atoms, the second of four times as many oxygen atoms, and the third of twice as many potassium atoms, the systems being so arranged that the sulphur system is always centrally situated with respect to the other two, and the potassium system so that it would affect the vertical axis, then it is obvious that the replacement of potassium by an element of greater atomic weight would specially increase the length of w (corresponding to the vertical axis), and cause a smaller increase in the horizontal parameters (x and 1/ '); moreover, the increments would advance with the atomic weight of the replacing metal.
A pupil of Nessus, or, as some accounts prefer, of Democritus himself, he was a complete sceptic. He accepted the Democritean theory of atoms and void and the plurality of worlds, but held a theory of his own that the stars are formed from day to day by the moisture in the air under the heat of the sun.
The acetyl compound on reduction yields two of its nitrogen atoms in the form of ammonia and the third in the form of methylamine.
THIAZOLES, in organic chemistry, a series of heterocyclic compounds containing the grouping shown below; the replaceable hydrogen atoms in which are designated a, (3 and µ.
The cyanhydrin is hydrolysable to an acid, the lactone of which may be reduced by sodium amalgam to a glucoheptose, a non-fermentable sugar containing seven carbon atoms. By repeating the process a non-fermentable gluco-octose and a fermentable glucononose may be prepared.
Lowry and Armstrong represent these compounds by the following spatial formulae which postulate a y-oxidic structure, and 5 asymmetric carbon atoms, i.e.
Since that date it has more than once been suggested that the molecular currents producing magnetism might be due to the revolution of one or more of the charged atoms or " ions " constituting the molecule.
It has been supposed that certain electrons revolve like satellites in orbits around the atoms with which they are associated, a view which receives strong support from the phenomena of the Zeeman effect, and on this assumption a theory has been worked out by P. Langevin, 2 which accounts for many, of the observed facts of magnetism.
As a consequence of the structure of the molecule, which is an aggregation of atoms, the planes of the orbits around the latter may be oriented in various positions, and the direction of revolution may be right-handed or left-handed with respect to the direction of any applied magnetic field.
If the structure of the molecule is so perfectly symmetrical that, in the absence of any external field, the resultant magnetic moment of the circulating electrons is zero, then the application of a field, by accelerating the right-handed (negative) revolutions, and retarding those which are left-handed, will induce in the substance a resultant magnetization opposite in direction to the field itself; a body composed of such symmetrical molecules is therefore diamagnetic. If however the structure of the molecule is such that the electrons revolving around its atoms do not exactly cancel one another's effects, the molecule constitutes a little magnet, which under the influence of an external field will tend to set itself with its axis parallel to the field.
It abolished the conception of life s an entity above and beyond the common properties of matter, and led to the conviction that the marvellous and exceptional qualities of that which we call " living " matter are nothing more nor less than an exceptionally complicated development of those chemical and physical properties which we recognize in a gradually ascending scale of evolution in the carbon compounds, containing nitrogen as well as oxygen, sulphur and hydrogen as constituent atoms of their enormous molecules.
TRIAZINES, in organic chemistry, a series of cyclic compounds, containing a ring system composed of three carbon and three nitrogen atoms. Three series are possible, the positions of Marine Trias Of The Alpine And Indian Types.
Piperic acid differs from piperonylic acid by the group C4H 4, and it was apparent that these carbon atoms must be attached to the carbon atom which appears in the carboxyl group of piperonylic acid, for if they were directly attached to the benzene ring polycarboxylic acids would result in oxidation.
Crum was probably the first to recognize that some hydrogen atoms of the cellulose had been replaced by an oxide of nitrogen, and this view was supported more or less by other workers, especially Hadow, who appears to have distinctly recognized that at least three compounds were present, the most violently explosive of which constituted the main bulk of the product commonly obtained and known as guncotton.
He introduced a system which, so far as we know, was his own, though founded upon the Epicurean philosophical creed; on the practical side it conformed pretty closely to the Stoic rule of life, thus adapting itself to the leanings of the better stamp of Romans in the later times of the republic. According to Asclepiades all diseases depended upon alterations in the size, number, arrangement or movement of the "atoms," of which, according to the doctrine of Epicurus, the body consisted.
These atoms were united into passages (iropot) through which the juices of the body were conveyed.
The organic derivatives of silicon resemble the corresponding carbon compounds except in so far that the silicon atom is not capable of combining with itself to form a complex chain in the same manner as the carbon atom, the limit at present being a chain of three silicon atoms. Many of the earlier-known silicon alkyl compounds were isolated by Friedel and Crafts and by Ladenburg, the method adopted consisting in the interaction of the zinc alkyl compounds with silicon halides or esters of silicic acids.
He held the doctrine that the chemical elements are compounds of equal and similar atoms, and might therefore possibly be all derived from one generic atom.
The first term includes simple sugars containing two to nine atoms of carbon, which are known severally as bioses, trioses, tetroses, pentoses, hexoses, &c.; whilst those of the second group have the formula C12H22011 and are characterized by yielding two monosaccharose molecules on hydrolysis.
The facts suggested that the six carbon atoms formed a chain, and that a hydroxy group was attached to five of them, for it is very rare for two hydroxy groups to be attached to the same carbon atom.
It is seen that aldoses and ketoses which differ stereochemically in only the two final carbon atoms must yield the same osazone; and since d-mannose, d-glucose, and d-fructose do form the same osazone (d-glucosazone) differences either structural or stereochemical must be placed in the two final carbon atoms.3 It may here be noticed that in the sugars there are asymmetric carbon atoms, and consequently optical isomers are to be expected.
Thus glucose, containing four such atoms, can exist in 16 forms; and the realization of many of these isomers by E.
The plane projection of molecular structures which differ stereochemically is discussed under Stereoisomerism; in this place it suffices to say that, since the terminal groups of the hexaldose molecule are different and four asymmetric carbon atoms are present, sixteen hexaldoses are possible; and for the hexahydric alcohols which they yield on reduction, and the tetrahydric dicarboxylic acids which they give on oxidation, only ten forms are possible.
When such compounds are converted into corresponding dibasic acids, CO 2 H.[CH(OH)) 3.00 2 H, the number of asymmetric carbon atoms becomes reduced from three to two, as the central carbon atom is then no longer associated with four, but with only three different radicles.
This formula, which necessitates the presence of two asymmetric carbon atoms in an alkyl tetrahydroberberine, has been accepted by M.
AMINES, in chemistry, derivatives of ammonia in which one or more of the hydrogen atoms are replaced by alkyl or aryl groups.
The replacement of one hydrogen atom by one alkyl or aryl group gives rise to primary amines; of two hydrogen atoms by two groups, to secondary amines; of three hydrogen atoms by three groups, to tertiary amines.
His theory of light and theory of the cosmic atoms were equally astonishing.
The isomerism which occurs as soon as the molecule contains a few carbon atoms renders any classification based on empirical molecular formulae somewhat ineffective; on the other hand, a scheme based on molecular structure would involve more detail than it is here possible to give.
Thus primary alcohols and aldehydes, both of the aliphatic and aromatic series, readily yield on oxidation acids containing the same number of carbon atoms. These reactions may be shown thus: - ï¿½ Rï¿½CH 2 OH -> R.
He had a great master in Democritus, the originator of the doctrine of atoms, and there is every reason to believe that the various " asclepia " were very carefully conducted hospitals for the sick, possessing a curious system of case-books, in the form of votive tablets, left by the patients, on which were recorded the symptoms, treatment and result of each case.
" Atom " has mainly a chemical import, being defined as the smallest particle of matter which can take part in a chemical reaction; a " molecule " is composed of atoms, generally two or more.
The doctrine that matter can be divided into, or regarded as composed of, discrete particles (termed " atoms " by early writers, and " molecules " by modern ones) has at all times played an important part in metaphysics and natural science.
The atomic theory is a theory of the constitution of bodies which asserts that they are made up of atoms. The opposite theory is that of the homogeneity and continuity of bodies, and asserts, at least in the case of bodies having no apparent organization, such, for instance, as water, that as we can divide a drop of water into two parts which are each of them drops of water, so we have reason to believe that these smaller drops can be divided again, and the theory goes on to assert that there is nothing in the nature of things to hinder this process of division from being repeated over and over again, times without end.
This is the doctrine of the infinite divisibility of bodies, and it is in direct contradiction with the theory of atoms.
" In modern times the study of nature has brought to light many properties of bodies which appear to depend on the magnitude and motions of their ultimate constituents, and the question of the existence of atoms has once more become conspicuous among scientific inquiries.
" We shall begin by stating the opposing doctrines of atoms and of continuity.
The atoms, they said, do not fill up the universe; there are void spaces between them.
Descartes, consistently with this doctrine, denies the existence of atoms as parts of matter, which by their own nature are indivisible.
To the atomist the true method of estimating the quantity of matter in a body is to count the atoms of it.
The void spaces between the atoms count for nothing.
According to Boscovich matter is made up of atoms. Each atom is an indivisible point, having position in space, capable of motion in a continuous path, and possessing a certain mass, whereby a certain amount of force is required to produce a given change of motion.
Besides this the atom is endowed with potential force, that is to say, that any two atoms attract or repel each other with a force depending on their distance apart.
Boscovich himself, in order to obviate the possibility of two atoms ever being in the same place, asserts that the ultimate force is a repulsion which increases without limit as the distance diminishes without limit, so that two atoms can never coincide.
This opinion is deduced from our experience of the behaviour of bodies of sensible size, but we have no experimental evidence that two atoms may not sometimes coincide.
This is a prejudice of the same kind with the last, arising from our experience of bodies consisting of immense multitudes of atoms.
No other system of atoms can occupy the same region of space at the same time, because before it could do so the mutual action of the atoms would have caused a repulsion between the two systems insuperable by any force which we can command.
In this way Boscovich explained the apparent extension of bodies consisting of atoms, each of which is devoid of extension.
When two bodies are said in ordinary language to be in contact, all that is meant is that they are so near together that the repulsion between the nearest pairs of atoms belonging to the two bodies is very great.
Atoms are endowed with the power of acting on one another by attraction or repulsion, the amount of the force depending on the distance between them.
It has not the so-called property, of Impenetrability, for two atoms may exist in the same place.
In like manner, after the French mathematicians had attempted, with more or less ingenuity, to construct a theory of elastic solids from the hypothesis that they consist of atoms in equilibrium under the action of their mutual forces, Stokes and others showed that all the results of this hypothesis, so far at least as they agreed with facts, might be deduced from the postulate that elastic bodies exist, and from the hypothesis that the smallest portions into which we can divide them are sensibly homogeneous.
Thomson (Lord Kelvin) to form a theory of vortex atoms in a homogeneous, incompressible and frictionless liquid."
When chemical phenomena occur the molecule may be divided into atoms, and these atoms, in the presence of electrical phenomena, may themselves be further divided into electrons or corpuscles.
In the light of these results it is of extreme significance that the four gases for which n = o are all believed to be monatomic: the molecules of these gases consist of single atoms. Moreover, these four are the only monatomic gases for which the value of y is known, so that the only atoms of which the shape can be determined are found to be spherical.
Now this is exactly the shape which we should expect to find in molecules composed of two spherical atoms distorting one another by their mutual forces, and all gases for which n=2 are diatomic.
If a solid body is regarded as an aggregation of similar atoms each of mass m, its specific heat C is given, as in formula (19) by C = i (n+3) R/Jm.
From Dulong and Petit's law that Cm is the same for all elements, it follows that n+3 must be the same for all atoms. Moreover, the value of Cm shows that n+3 must be equal to six.
Now if the atoms are regarded as points or spherical bodies oscillating about positions of equilibrium, the value of n+3 is precisely six, for we can express the energy of the atom in the form (9 2 v a 2 v a2v E = z(mu 2 +mv 2 +mw 2 +x 2 ax2 + y2ay2-fz2az2), where V is the potential and x, y, z are the displacements of the atom referred to a certain set of orthogonal axes.
The difficulty is further diminished when it is proved, as it can be proved, 2 that the modes of energy represented in the atomic spectrum acquire energy so slowly that the atom might undergo collisions with other atoms for centuries before being set into oscillations which would possess an appreciable amount of energy.
empiricism in the metaphysical system of Leibnitz, whose theory of self-determined monads can be understood only when taken in the light of the assertion of the rights of the subject against the substance of Spinoza and the atoms of the materialist.
These antinomies are four - two mathematical, two dynamical - connected with (I) the limitation of the universe in respect of space and time, (2) the theory that the whole consists of indivisible atoms (whereas, in fact, none such exist), (3) the problem of freedom in relation to universal causality, (4) the existence of a universal being - about each of which pure reason contradicts the empirical, as thesis and antithesis.
If material systems are constituted of discrete atoms, separated from each other by many times the diameter of any of them, this simple plan of exhibiting their interactions in terms of direct forces between them would indeed be exact enough to apply to a wide range of questions, provided we could be certain that the laws of the forces depended only on the positions and not also on the motions of the atoms. The most important example of its successful application has been the theory of capillary action elaborated by P. S.
Now this doctrine of material atoms is an almost necessary corollary to the doctrine of a universal aether.
The other course is to consider matter as formed of ultimate atoms, each the nucleus or core of an intrinsic modification impressed on the surrounding region of the aether; this might conceivably be of the nature of vortical motion of a liquid round a ring-core, thus giving a vortex atom, or of an intrinsic strain of some sort radiating from a core, which would give an electric atom.
We recognize an atom only through its physical activities, as manifested in its interactions with other atoms at a distance from it; this field of physical activity would be identical with the surrounding field of aethereal motion or strain that is inseparably associated with the nucleus, and is carried on along with it as it moves.
To make room for these we have to remember that the atomic nucleus has remained entirely undefined and beyond our problem; so that what may occur, say when two molecules come into close relations, is outside physical science - not, however, altogether outside, for we know that when the vital nexus in any portion of matter is dissolved, the atoms will remain, in their number, and their atmospheres, and all inorganic relations, as they were before vitality supervened.
Our direct knowledge of matter can, however, never be more than a rough knowledge of the general average behaviour of its molecules; for the smallest material speck that is sensible to our coarse perceptions contains myriads of atoms. The properties of the most minute portion of matter which we can examine are thus of the nature of averages.
We may gradually invent means of tracing more and more closely the average drifts of translation or orientation, or of changes of arrangement, of the atoms; but there will always remain an unaveraged residue devoid of any recognized regularity, which we can only estimate by its total amount.
The aether is taken to be at rest; and the strain-forms belonging to the atoms are the electric fields of the intrinsic charges, or electrones, involved in their constitution.
When the atoms are in motion these strain-forms produce straining and unstraining in the aether as they pass across it, which in its motional or kinetic aspect constitutes the resulting magnetic field; as the strains are slight the coefficient of ultimate inertia here involved must be great.
PYRAZINES, PIAZINES, or Paradiazines, In organic chem istry, a group of compounds containing a ring system composed of 4 carbon, atoms and 2 nitrogen atoms, the nitrogen atoms being in the para position.
The 2.3 derivatives are somewhat unstable compounds, since on heating they readily give up two hydrogen atoms. Tetrahydropyrazines of the 1.2.
His speculum metal is composed of four atoms of copper (126.4 parts) and one of tin (58.9 parts), a brilliant alloy, which resists tarnish better than any other compound tried.
OLEFINE, in organic chemistry, the generic name given to open chain hydrocarbons having only singly and doubly linked pairs of carbon atoms. The word is derived from the French olefiant (from olefier, to make oil), which was the name given to ethylene, the first member of the series, by the Dutch chemists, J.
The simple olefines containing one doublylinked pair of carbon atoms have the general formula (CnH2n; the di-olefines, containing two doubly-linked pairs, have the general formula C0H2n_2 and are consequently isomeric with the simple acetylenes.
As unsaturated compounds they can combine with two monovalent atoms. Hydrogen is absorbed readily at ordinary temperature in the presence of platinum black, and paraffins are formed; the halogens (chlorine and bromine) combine directly with them, giving dihalogen substituted compounds; the halogen halides to form monohalogen derivatives (hydriodic acid reacts most readily, hydrochloric acid, least); and it is to be noted that the haloid acids attach themselves in such a manner that the halogen atom unites itself to the carbon atom which is in combination with the fewest hydrogen atoms (W.
QUINONES, in organic chemistry, a group of compounds in which two hydrogen atoms of a benzene nucleus are replaced by two oxygen atoms. This replacement may take place either in the ortho or para positions, giving rise to orthoquinones or to paraquinones; metaquinones do not appear to have been isolated.
It combines directly with two and four atoms of bromine.
In 1815 he published anonymously in the Annals of Philosophy a paper "On the relation between the specific gravities of bodies in their gaseous state and the weights of their atoms," in which he calculated that the atomic weights of a number of the elements are multiples of that of hydrogen; and in a second paper published in the same periodical the following year he suggested that the rrpcbrn iiXrl of the ancients is realized in hydrogen, from which the other elements are formed by some process of condensation or grouping.
Bunsen first announced their discovery, for according to their view every combination of an element showed the characteristic spectrum of its constituent atoms; it did not matter according to this view whether a salt,' e.g.
In both cases an increased number of carbon atoms increases the absorption at the most refrangible end.
He determined that definite absorption bands are only produced by substances in which three pairs of carbon atoms are doubly linked together, as in the benzene ring.
While Leucippus's notion of Being agreed generally with that of the Eleatics, he postulated its plurality (atoms) and motion, and the reality of not-Being (the void) in which his atoms moved.
He not only agrees with Laplace and Lyell about the evolution of the solar system, but also supposes that the affinities, pointed out by Lothar Meyer and Mendeleeff, between groups of chemical elements prove an evolution of these elements from a primitive matter (prothyl) consisting of homogeneous atoms. These, however, are not ultimate enough for him; he thinks that everything, ponderable and imponderable or ether, is evolved from a primitive substance, which condenses first into centres of condensation (pyknatoms), and then into masses, which when they exceed the mean consistency become ponderables, and when they fall below it become imponderables.
He supposes that aesthesis and tropesis, as rudimentary sensation and will, are the very causes of condensation; that they belong to pyknatoms, to ponderables and imponderables, to chemical atoms and molecules.
It appears to his imagination that the affinity of two atoms of hydrogen to one of oxygen, the attraction of the spermatozoon to the ovum, and the elective affinity of d pair of lovers are all alike due to sensation and will.
In his Belfast address (1874), while admitting that matter as understood by Democritus is insufficient, because atoms without sensation cannot be imagined to produce sensation, he contended, nevertheless, that matter properly understood is " the promise and potency of all terrestrial life."
His theory of bodies involved an idealistic analysis neither into bodily atoms nor into mathematical units, but into mentally endowed simple substances.
For a time, under the influence of Fechner's Psychophysics, he thought that Nature has two sides, a physical and a psychological, and added that all atoms have feeling.
If he has any originality, it consists in substituting for the association of ideas the " economy of thinking," by which he means that all theoretical conceptions of physics, such as atoms, molecules, energy, &c., are mere helps to facilitate our consideration of things.
According to him, whatever inferences we make, certain or uncertain, are mere economies of thought, adapting ideas to sensations, and filling out the gaps of experience by ideas; whatever we infer, whether bodies, or molecules, or atoms, or space of more than three dimensions, are all without distinction equally provisional conceptions, things of thought; and " bodies or things are compendious mental symbols for groups of sensations - symbols which do not exist outside thought."
atoms, which are never given to any consciousness, he returns the familiar Kantian answer that, though unperceived, they are perceptible.
atoms. But he limits psychological and ontological " ideals " entirely to imaginary transcendence, The result is that he confines metaphysical transcendence to " a process into the imaginary " as regards the substantial and causal content of cosmological " ideals," and altogether as regards psychological and ontological " ideals."
The study of the structure of atoms has suggested a connexion of mass with electrical phenomena which implies its dependence on motion; but this is not inconsistent with the observed fact of its practical constancy, to a high degree of accuracy, for bodies composed of atoms.
But from a study of Dalton's own MS. laboratory notebooks, discovered in the rooms of the Manchester society, Roscoe and Harden (A New View of the Origin of Dalton's Atomic Theor y, 1896) conclude that so far from Dalton being led to the idea that chemical combination consists in the approximation of atoms of definite and characteristic weight by his search for an explanation of the law of combination in multiple proportions, the idea of atomic structure arose in his mind as a purely physical conception, forced upon him by study of the physical properties of the atmosphere and other gases.
He proceeds to give what has been quoted as his first table of atomic weights, but on p. 248 of his laboratory notebooks for 1802-1804, under the date 6th of September 1803, there is an earlier one in which he sets forth the relative weights of the ultimate atoms of a number of substances, derived from analysis of water, ammonia, carbon-dioxide, &c. by chemists of the time.
de Phys., 1811), in which he enunciated the hypothesis known by his name (Avogadro's rule) that under the same conditions of temperature and pressure equal volumes of all gases contain the same number of smallest particles or molecules, whether those particles consist of single atoms or are composed of two or more atoms of the same or different kinds.
On such a hypothesis, the relatively unstable normal diazo hydroxides would be the syn-compounds, since here the nitrogen atoms would be more easily eliminated, whilst the stable iso-diazo derivatives would be the anti-compounds, thus: R N R N HO-N N OH Normal hydroxide Iso hydroxide (Syn-compound) (Anti-compound) In support of this theory, Hantzsch has succeeded in isolating a series of syn - and anti-diazo-cyanides and -sulphonates (Ber.,1895,28, p.666; 1900, 33, P. 2161; 1901, 34, p. 4166).
The constitution of the diazo fatty esters is inferred from the fact that the two nitrogen atoms, when split off, are replaced by two monovalent elements or groups, thus leading to the formula N >CH CO 2 C 2 H 5, for diazoacetic ester.
These phenomena were quite in accordance with the atomic conception of matter, since a compound containing the same number of atoms of carbon, nitrogen, oxygen and hydrogen as another in the same weight might differ in internal structure by different arrangements of those atoms. Even in the time of Berzelius the newly introduced conception proved to include two different groups of facts.
the vapour densities of the isomers were the same, as in butylene and isobutylene, to take the most simple case; here the molecular conception admits that the isolated groups in which the atoms are united, i.e.
the molecules, are identical, and so the molecule of both butylene and isobutylene is indicated by the same chemical symbol C4118, expressing that each molecule contains, in both cases, four atoms of carbon (C) and eight of hydrogen (H).
In the case of metamerism we can imagine that the atoms are differently linked, say in the case of butylene that the atoms of carbon are joined together as a continuous chain, expressed by CC C C, normally as it is called, whereas in isobutylene the fourth atom of carbon is not attached to the third but to the second carbon atom, i.e.
that atoms attached to carbon, to express it in the atomic style, cling more intensely to it than, for instance, when combined with oxygen.
the conception as to the order in which the atoms composing a molecule are linked together.
By Wilhelm Ostwald especially, attempts have been made to substitute the notion of atoms and molecular structure by less hypothetical conceptions; these ideas may some day receive thorough confirmation, and when this occurs science will receive a striking impetus.
Considering the hydrocarbons given by the general formula C x H y, the internal linkages of the carbon atoms need at least xi bonds, using up 2(xI) valencies of the 4x to be accounted for, and thus leaving no more than 2(x-11) for binding hydrogen: a compound C 3 H 9 is therefore impossible, and indeed has never been met.
Considering the predicted series of compounds C7,H2,,+2, which is the well-known homologous series of methane, the first member, the possible of isomerism lies in that of a different linking of the carbon atoms. This first presents itself when four are present, i.e.
The third most valuable indication which molecular structure gives about these isomers is how to prepare them, for instance, that normal hexane, represented by CH 3 CH 2 CH 2 CH 2 CH 2 CH3, may be obtained by action of sodium on propyl iodide, CH 3 CH 2 CH 2 I, the atoms of iodine being removed from two molecules of propyl iodide, with the resulting fusion.
of the two systems of three carbon atoms into a chain of six carbon atoms. But it is not only the formation of different isomers which is included in their constitution, but also the different ways in which they will decompose or give other products.
Now in oxidizing, or introducing more oxygen, for instance, by means of a mixture of sulphuric acid and potassium bichromate, and admitting that oxygen acts on both compounds in analogous ways, the two alcohols may give (as they lose two atoms of hydrogen) CH 3 CH 2 COH and CH 3 C0 CH 3.
In this equation a relates to molecular attraction; and it is not improbable that in isomeric molecules, containing in sum the same amount of the same atoms, those mutual attractions are approximately the same, whereas the chief difference lies in the value of b, that is, the volume occupied by the molecule itself.
For what reason this volume may differ from case to case lies close at hand; in connexion with the notion of negative and positive atoms, like chlorine and hydrogen, experience tends to show that the former, as well as the latter, have a mutual repulsive power, but the former acts on the latter in the opposite sense; the necessary consequence is that, when those negative and positive groups are distributed in the molecule, its volume will be smaller than if the negative elements are heaped together.
Now taking the isomers H 3 C CC1 3 (M„ = 108) and C1H 2 C CHC1 2 (M„ = we see the negative chlorine atoms heaped up in the left hand formula, but distributed in the second; the former therefore may be presumed to occupy a larger space, the molecular volume, that is, the volume in cubic centimetres occupied by the molecular weight in grams, actually being 108 in the former, and 103 in the latter case (compare Chemistry: Physical).
ESTERS, in organic chemistry, compounds formed by the condensation of an alcohol and an acid, with elimination of water; they may also be considered as derivatives of alcohols, in which the hydroxylic hydrogen has been replaced by an acid radical, or as acids in which the hydrogen of the carboxyl group has been replaced by an alkyl or aryl group. In the case of the polybasic acids, all the hydrogen atoms can be replaced in this way, and the compounds formed are known as "neutral esters."
Radium itself emits three types of rays: (1) the a rays, which are regarded as positively charged helium atoms; these rays are stopped by a single sheet of paper; (2) the s rays, which are identified with the cathode rays, i.e.
Frankland, when in 1858 Kekule published a paper in which, after giving reasons for regarding carbon as a tetravalent element, he set forth the essential features of his famous doctrine of the linking of atoms. He explained that in substances containing several carbon atoms it must be assumed that some of the affinities of each carbon atom are bound by the affinities of the atoms of other elements contained in the substance, and some by an equal number of the affinities of the other carbon atoms. The simplest case is when two carbon atoms are combined so that one affinity of the one is tied to one affinity of the other; two, therefore, of the affinities of the two atoms are occupied in keeping the two atoms together, and only the remaining six are available for atoms of other elements.
Some writers have supposed that the ultimate atoms are conductors, and that heat is transferred through them when they are in contact.
Weber's hypothesis of electric atoms, capable of diffusing through metallic bodies and conductors of electricity, but capable of vibration only in non-conductors, it is possible that the ultimate mechanism of conduction may be reduced in all cases to that of diffusion in metallic bodies or internal radiation in dielectrics.
The high conductivity of metals is then explained by the small mass and high velocity of diffusion of these electric atoms. Assuming the kinetic energy of an electric atom at any temperature to be equal to that of a gaseous molecule, its velocity, on Sir J.
The fundamental postulates of Epicureanism are atoms and the void (iiroya Kai Kevov).
Space is infinite, and there is an illimitable multitude of indestructible, indivisible and absolutely compact atoms in perpetual motion in this illimitable space.
These atoms, differing only in size, figure and weight, are perpetually moving with equal velocities, but at a rate far surpassing our conceptions; as they move, they are for ever giving rise to new worlds; and these worlds are perpetually tending towards dissolution, and towards a fresh series of creations.
Even in the movement of the atoms he introduces a sudden change of direction, which is supposed to render their aggregation easier, and to break the even law of destiny.
The chlorine is not completely precipitated by silver nitrate in nitric acid solution, the ionization apparently not proceeding to all the chlorine atoms. Thallic iodide, T11 3, is interesting on account of its isomorphism with rubidium and caesium tri-iodides, a resemblance which suggests the formula T11 (12) for the salt, in which the metal is obviously monovalent.
It acts as a powerful oxidizing agent, both in acid and alkaline solution; in the first case two molecules yield five atoms of available oxygen and in the second, three atoms: 2KMnO 4 +3H 2 SO 4 = K2S04+2MnS04+3H20+50; 2KMnO 4 +3H 2 O =2Mn02 H20+2KHO+30.
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