In simple substances like potassium chloride it seems evident that one kind of dissociation only is possible.
These colour changes are connected with a dissociation of the molecules.
They are yellowish-red solids, which behave as weak bases, their salts undergoing hydrolytic dissociation in aqueous solution.
The history of its dissociation is connected with that of the class, viz.
The result of this treatment is that the comparatively heavy oils undergo dissociation, as shown by the experiments of Thorpe and Young, into specifically lighter hydrocarbons of lower boiling points, and the yield of kerosene from ordinary crude petroleum may thus be greatly increased.
(I) In very dilute solutions of simple substances, where only one kind of dissociation is possible and the dissociation of the ions is complete, the number of pressure-producing particles necessary to produce the observed osmotic effects should be equal to the number of ions given by a molecule of the salt as shown by its electrical properties.
(2) As the concentration of the solutions increases, the ionization as measured electrically and the dissociation as measured osmotically might decrease more or less together, though, since the thermodynamic theory only holds when the solution is so dilute that the dissolved particles are beyond each other's sphere of action, there is much doubt whether this second relation is valid through any appreciable range of concentration.
The specific rotation also varies with the concentration; this is due to the dissociation of complex molecules into simpler ones, a view confirmed by cryoscopic measurements.
There he remained for thirteen years, and it was during this period that he devised his well-known method for determining vapour densities, and carried out his experiments on the dissociation of the halogens.
Boric acid (q.v.) being only a weak acid, its salts readily undergo hydrolytic dissociation in aqueous solution, and this property can be readily shown with a concentrated aqueous solution of borax, for by adding litmus and then just sufficient acetic acid to turn the litmus red, the addition of a large volume of water to the solution changes the colour back to blue again.
It does not dissociate on heating as do the pentachloride and pentabromide, thus indicating the existence of pentavalent phosphorus in a gaseous compound; dissociation, however, into the trifluoride and free fluorine may be brought about by induction sparks of 150 to 200 mm.
Deviation from this rule indicates molecular dissociation or association.
In neutral, and still more in acid solutions, the dissociation of the indicator is practically nothing, and the liquid is colourless.
Let us consider the case of the neutralization of a base by an acid in the light of the dissociation theory.
C. Jones, The Theory of Electrolytic Dissociation (New York, 1900); N.
Diseases of the latter kind are especially interesting, as in them we see that parts of the nervous structure, separated in space, may nevertheless be associated in function; for instance, wasting of a group of muscles associated in function may depend on a set of central degenerations concurring in parts whose connexion, in spite of dissociation in space, we thus perceive.
On the other hand, they are much weaker bases than the aliphatic amines, their salts undergoing hydrolytic dissociation in aqueous solution.
There must be considerable dissociation of molecules, and as a first approximation it may be taken that of io molecules of most of the components about 9 (or in the case of magnesium sulphate 5) have been separated into their ions, and that it is only during slow concentration as in a natural saline that the ions combine to produce the various salts in the proportions set out in the above table.
This takes place when in the manufacture of the carbide the material is kept too long in contact with the arc, since this overheating causes the dissociation of some of the calcium carbide and the solution of metallic calcium in the remainder.
DISSOCIATION, a separation or dispersal, the opposite of association.
Electrolytic or ionic dissociation is the separation of a substance in solution into ions.
Carbon dioxide dissociates, when strongly heated, into carbon monoxide and oxygen, the reaction being a balanced action; the extent of dissociation for varying temperatures and pressures has been calculated by H.
The alkali and alkaline earth cyanides are soluble in water and in alcohol, and their aqueous solution, owing to hydrolytic dissociation, possesses an alkaline character.
In many of these cases the observed facts might perhaps be explained by dissociation, the undissociated compound producing no marked effect on the spectra.
It is one of the "weak" acids, its dissociation constant being only 0.0 8 169 (J.
From the osmotic side also, then, electrolytic dissociation is indicated, and indeed, it was from this side that the idea was first suggested by S.
It was soon discovered that the faculty of inducing dissociation possessed by the current might now be utilized with some hope of pecuniary success, but as electrolytic currents are of lower voltage than those required in electric furnaces, molten alumina again became impossible.
The operation is essentially a dissociation of alumina into aluminium, which collects at the cathode, and into oxygen, which combines with the anodes to form carbon monoxide, the latter escaping and being burnt to carbon dioxide outside.
The dissociation of the hybrid element in a plant must be obviated by careful selection.
All thallium compounds volatile or liable to dissociation at the temperature of the flame of a Bunsen lamp impart to such flame an intense green colour.
For strong solutions the discrepancies from Raoult's law often become very large, even if dissociation is allowed for.
Vapour density determinations indicate that dissociation occurs when the vapour is heated above the boiling point.
The theory of the ionization of salts in solution has raised much discussion amongst chemists, but the general fact is certain that electricity only moves through liquids in association with matter, and simultaneously involves chemical dissociation of molecular groups.
From 1865 onwards he treated this question in several papers, and in particular maintained the dissociation of vapour of chloral hydrate, in opposition to H.
Ostwald, among other chemists, in support of the hypothesis of electrolytic dissociation in solutions.
It boils at 290°, forming a colourless vapour which just about the boiling-point corresponds in density to tetratomic molecules, P4; at 1500° to 1700°, however, Biltz and Meyer detected dissociation into P2 molecules.
Wharfinger states that in chlorosis the specific action of iron is only obtained by administering those inorganic preparations which give a reaction with the ordinary reagents; the iron ions in a state of dissociation act as a catalytic agent, destroying the hypothetical toxin which is the cause of chlorosis.
It is possible that in complicated organic substances we might have two kinds of dissociation, electrical and non-electrical, occurring simultaneously, while the possibility of the association of molecules accompanied by the electrical dissociation of some of them into new parts should not be overlooked.
The dissociation theory was originally suggested by the osmotic pressure relations.
The ratios of the coagulative powers can thus be calculated to be i: x: x 2, and putting x =32 we get I: 32: 1024, a satisfactory agreement with the numbers observed.4 The question of the application of the dissociation theory to the case of fused salts remains.
While it seems clear that the conduction in this case is carried on by ions similar to those of solutions, since Faraday's laws apply equally to both, it does not follow necessarily that semi-permanent dissociation is the only way to explain the phenomena.
The evidence in favour of dissociation in the case of solutions does not apply to fused salts, and it is possible that, in their case, a series of molecular interchanges, somewhat like Grotthus's chain, may represent the mechanism of conduction.
In the case of substances like ammonia and acetic acid, where the dissociation is very small, I - a is nearly equal to unity, and only varies slowly with dilution.
Van 't Hoff's formula is equivalent to taking the frequency of dissociation as proportional to the square of the concentration of the molecules, and the frequency of recombination as proportional to the cube of the concentration of the ions.
When the solutions of two substances are mixed, similar considerations to those given above enable us to calculate the resultant changes in dissociation.
The two solutions, then, will so act on each other when mixed that they become isohydric. Let us suppose that we have one very active acid like hydrochloric, in which dissociation is nearly complete, another like acetic, in which it is very small.
The dissociation theory gives an immediate explanation of the fact that, in general, no heat-change occurs when two neutral salt solutions are mixed.
Since the salts, both before and after mixture, exist mainly as dissociated ions, it is obvious that large thermal effects can only appear when the state of dissociation of the products is very different from that of the reagents.
But his best known contribution to general chemistry is his work on the phenomena of reversible reactions, which he comprehended under a general theory of " dissociation.
We may therefore reasonably assume that the limiting values of the specific heats at zero pressure do not vary with the temperature, provided that the molecule is stable and there is no dissociation.
The Energy Of Vibration May Be Appreciable At Ordinary Temperatures, And Would Probably Increase More Rapidly Than That Of Translation With Rise Of Temperature, Especially Near A Point Of Dissociation.
While working on the olefines he noticed that a change takes place in the density of the vapour of amylene hydrochloride, hydrobromide, &c., as the temperature is increased, and in the gradual passage from a gas of approximately normal density to one of half-normal density he saw a powerful argument in favour of the view that abnormal vapour densities, such as are exhibited by sal-ammoniac or phosphorus pentachloride, are to be explained by dissociation.
Paterno and Nasini, however, detected dissociation.
It sublimes when heated, but under pressure it melts at 148°, giving a normal vapour density, but on further heating it dissociates into the trichloride and chlorine; this dissociation may be retarded by vapourizing in an atmosphere of chlorine.
Vapour density determinations at 448° indicate a partial dissociation of the double molecule Fe2Cl6I on stronger heating it splits into ferrous chloride and chlorine.
The vapour density is 10.6 (air =1) at 564° C., corresponding to a tetratomic molecule As; at a white heat the vapour density shows a considerable lowering in value, due to the dissociation of the complex molecule.
He had an affinity for opioid receptors and a slow dissociation from them.
Dissociation of core particles into open core and genomic RNA The open core particles devoid of genomic dsRNAs were isolated by centrifugation through CsTFA.
converge to zero at the dissociation limit?
They may have a role in dissociation of tubulin dimers.
dissociation of sensibility.
dissociation of DNA molecules which in turn can lead to gene mutations.
dissociation of water.
This in turn involves bond dissociation, gain of an electron by the halogen, and hydration of the halide ion.
In some cases, effective reorganization can decrease task difficulty, implying a dissociation between frontal activity and basic memory demand.
For the removal of H atoms, the method of sustained off-resonance irradiation collision-induced dissociation (SORI-CID) in FT-ICR has been applied.
If the effect is only one way we may call it a partial dissociation.
Consistent with the model, however, a sensitive psycholinguistic test, a lexical decision task, revealed a double dissociation between word groups.
The transfer effect in artificial grammar learning: A functional dissociation between two modes of classification.
Our results show a strong dissociation between two different tasks.
They seem to take both too seriously to allow such dissociation, and they want to use each for the enrichment of the other.
dissociation enthalpy " .
dissociation curve at a normal pH (pH = 7.4 ).
dissociation constants, strength of acids, concept of pH.
dissociation dynamics of these molecules.
Gaseous exchange at the tissues, partial pressure of gases, oxygen dissociation.
We are using FT-ICR MS (and specifically electron capture dissociation) along with molecular modeling to probe their gas phase structures.
In effect, it achieves its results by temporarily raising or lowering the bond dissociation energy.
dissolve upon the dissociation of a shareholder.
Published in January 2005 " Are there two qualitatively distinct forms of dissociation?
dorsal capsulodesis for scapholunate dissociation.
electrolytic dissociation of water molecules to hydrogen and oxygen with membrane separation.
The term we are using here should more accurately be called the " lattice dissociation enthalpy " .
Keywords: AIR, CONVERSION, FACTOR, UNIT, WATER Thermodynamic properties of air in dissociation equilibrium.
exciton dissociation at the polymer interface is energetically favorable.
heaviness in head and feelings of dissociation ).
This involves looking at catalytic dissociation of ammonia to hydrogen and nitrogen and also the selective catalytic oxidation of ammonia to nitrogen and water.
Dissociation of virtual photons in events with a leading proton at HERA.
retting process, the dissociation of these fibers from the core of the stem.
Arrhenius is specially associated with the development of the theory of electrolytic dissociation, and his great paper on the subject, Recherches sur la conductibilite galvanique des electrolytes - (1) conductibilite galvanique des solutions aqueuses extremement diluees, (2) theorie chimique des electrolytes, was presented to the Stockholm Academy of Sciences in 1883.
Chem., 1909, 6 9, p. 1 57), in a study of the dissociation isotherms over 300Ã‚°-850Ã‚°, detected molecules of Ss, S6 and S2, whilst S i appears to exist below pressures of 30 mm.
Sulphuretted hydrogen, H 2 S, a compound first examined by C. Scheele, may be obtained by heating sulphur in a current of hydrogen, combination taking place between 200Ã‚° C. and 358Ã‚° C., and being complete at the latter temperature, dissociation taking place above this temperature (M.
So far back as 1850 he also suggested a view which, in a modified form, is of fundamental importance in the modern theory of ionic dissociation, for, in a paper on the theory of the formation of ether, he urged that in an aggregate of molecules of any compound there is an exchange constantly going on between the elements which are contained in it; for instance, in hydrochloric acid each atom of hydrogen does not remain quietly in juxtaposition with the atom of chlorine with which it first united, but changes places with other atoms of hydrogen.
The abnormal specific heats of the halogen elements may be due to a loosening of the atoms, a preliminary to the dissociation into monatomic molecules which occurs at high temperatures.
The ordinary laws of chemical equilibrium have been applied to the case of the dissociation of a substance into its ions.
Electrolytic or ionic dissociation is the separation of a substance in solution into ions (see Electrolysis; Solution).
p. 670) that the velocity of formation of the amino-azo compound depends only on the nature of the reagents and not on the concentration, and that in coupling the hydrochloride of a tertiary amine with diazobenzene suiphonic acid the reaction takes place between the acid and the base set free by the hydrolytic dissociation of its salt, for the formation of the amino-azo compound, when carried out in the presence of different acids, takes place most rapidly with the weakest acid (H.
In the case of electrolytes we can go further, and calculate the diffusion constant itself from the theory of electrolytic dissociation (see Electric conduction, § In Liquids).
The constitution of the diazonium groupN 2 -X, may be inferred from the following facts :-The group C6H6N2-behaves in many respects similarly to an alkali metal, and even more so to the ammonium group, since it is capable of forming colourless neutral salts with mineral acids, which in dilute aqueous solution are strongly ionized, but do not show any trace of hydrolytic dissociation (A.
It boils at 290Ã‚°, forming a colourless vapour which just about the boiling-point corresponds in density to tetratomic molecules, P4; at 1500Ã‚° to 1700Ã‚°, however, Biltz and Meyer detected dissociation into P2 molecules.
It sublimes when heated, but under pressure it melts at 148Ã‚°, giving a normal vapour density, but on further heating it dissociates into the trichloride and chlorine; this dissociation may be retarded by vapourizing in an atmosphere of chlorine.
Vapour density determinations at 448Ã‚° indicate a partial dissociation of the double molecule Fe2Cl6I on stronger heating it splits into ferrous chloride and chlorine.
The orthodoxy which refuses all new theories may look for help to the pathological dissociation of personality, or at least (e.g.
The vapour density is 10.6 (air =1) at 564Ã‚° C., corresponding to a tetratomic molecule As; at a white heat the vapour density shows a considerable lowering in value, due to the dissociation of the complex molecule.
This study investigated one aspect of the retting process, the dissociation of these fibers from the core of the stem.
Some people also experience dissociation, which means they feel as though they are separate from their own body watching the trauma unfold once again.
Dissociative disorders-A group of mental disorders in which dissociation is a prominent symptom.
Because social and pragmatic deficits are core characteristics of autism, it is important to look for dissociation among language, social adaptive skills, and motor behavior.
Children with a specific learning disability, like children with severe mental retardation or autism, may present with dissociation in developmental skills.
Also, lack of academic success at school can reflect dissociation between academic achievement and general intellectual abilities.
Sulphuretted hydrogen, H 2 S, a compound first examined by C. Scheele, may be obtained by heating sulphur in a current of hydrogen, combination taking place between 200° C. and 358° C., and being complete at the latter temperature, dissociation taking place above this temperature (M.
The Chemistry of the Sun (1887) is an elaborate treatise on solar spectroscopy based on the hypothesis of elemental dissociation through the intensity of solar heat.
The primary products of the dissociation of albumins are the albumoses, characterized by not being coagulable by heat, more soluble than the albumins, having a far less complex composition, and capable of being " salted (7) out " by certain salts, and the peptones, similar to albumoses but not capable of being " salted out "; moreover, peptones are less complex than albumoses.
The dissociation theory refers this to the action of electric charges carried by the free ions.
In order that there should be no change in the states of dissociation on mixing, it is necessary, therefore, that the concentration of the hydrogen ions should be the same in each separate solution.
In the case of weaker acids, the dissociation of which is less complete, divergences from this constant value will occur, for some of the molecules have to be separated into their ions.
Compound bodies, we now know, have their own spectra, and only when dissociation occurs can the compound show the rays characteristic of the element: this perhaps was to be expected, but it came as a surprise and was not readily believed, that elements, as a rule, possess more than one spectrum according to the physical conditions under which they become luminous.
In every solid body there is a continual atomic dissociation, the result of which is that mixed up with the atoms of chemical matter composing them we have a greater or less percentage of free electrons.
The word usage examples above have been gathered from various sources to reflect current and historial usage. They do not represent the opinions of YourDictionary.com.