Acids Sentence Examples

It is readily soluble in warm dilute mineral acids forming cobaltous salts.

It is somewhat readily oxidized; nitric acid gives carbonic and oxalic acids, and chromic acid, carbonic and acetic acids.

The free acid, which is obtained by treating the salts with acids, is an oily liquid smelling like prussic acid; it is very explosive, and the vapour is poisonous to about the same degree as that of prussic acid.

The oxides of type RO are soluble in water, the solution possessing a strongly alkaline reaction and rapidly absorbing carbon dioxide on exposure; they are basic in character and dissolve readily in acids with the formation of the corresponding salts.

Phenol dissolves readily in concentrated sulphuric acid, a mixture of phenol-orthoand -para-sulphonic acids being formed.

It is readily decomposed by water with formation of sulphurous, sulphuric and thiosulphuric acids, with simultaneous liberation of sulphur.

It has already been stated that the heats of neutralization of acids and bases in aqueous solution are additively composed of two terms, one being constant for a given base, the other constant for a given acid.

Similarly, normal solutions of hydrochloric and nitric acids can be prepared.

It is an indigo-blue powder, soluble in hydrochloric acid, but insoluble in dilute nitric and sulphuric acids.

It is universally found that the weights of two bases which neutralize the same weight of one acid are equivalent in their power of neutralizing other acids.

The pentammine purpureo-salts are formed from the luteo-salts by loss of ammonia, or from an air slowly oxidized ammoniacal cobalt salt solution, the precipitated luteosalt being filtered off and the filtrate boiled with concentrated acids.

The 2.6-diketo-tetrahydropyrimidines or uracils may be considered as the ureides of /-aldehydo, and 0-ketonic acids.

Chlorophyll is not soluble in water, nor in acids or alkalies without decomposition.

The fate of these inorganiccompounds has not been certainly traced, but they give rise later on to the presence in the plant of various amino acid amides, such as leucin, glycin, asparagin, &c. That these are stages on the way to proteids has been inferred from the fact that when proteids are split up by various means, and especially by the digestive secretions, these nitrogen-containing acids are among the products which result.

The inability to enter the cells may be due to the lack of chemotactic bodies, to incapacity to form cellulose-dissolving enzymes, to the existence in the hostcells of antagonistic bodies which neutralize or destroy the acids, enzymes or poisons formed by the hyphae, or even to the formation and excretion of bodies which poison the Fungus.

The cell sap contains various substances in solution such as sugars, inulin, alkaloids, glucosides, organic acids and various inorganic salts.

Some of these have a neutral reaction, others react as feeble acids.

Carbolic acid is distinguished from all other acids so-called - except oxalic acid and hydrocyanic acid - in that it is a neurotic poison, having a marked action directly upon the nervous system.

It is a yellow, microcrystalline powder, soluble in water, alcohol and chloroform, and forming readily decomposed salts with acids.

Water decomposes it violently with formation of hydrochloric and sulphurous acids.

In many cases it acts as a reducing agent (when used in the presence of acids); thus, permanganates are reduced to manganous salts, iodates are reduced with liberation of iodine, &c., 2KMnO 4 + 550 2 + 2H 2 0 = K 2 SO 4 + 2MnSO 4 + 2H 2 SO 4; 2K103+ 550 2 + 4H 2 O =1 3 + 2KHSO 4 + 3H2S04.

It is decomposed by water into hydrofluoric and sulphurous acids.

Water decomposes it into hydrochloric and sulphurous acids.

It is a colourless, oily, fuming liquid which is decomposed by water into sulphuric and hydrochloric acids.

Both of these statements are correct when the powerful mineral acid and bases are considered, exceptions only arising when weak acids and bases are employed.

Silbermann, whose chief theoretical achievement was the recognition that the heat of neutralization of acids and bases was additively composed of two constants, one determined by the acid and the other by the base.

In addition to this, the further regularity has been observed that when the powerful monobasic acids are neutralized by the powerful monacid bases, the heat of neutralization is in all cases the same.

To him belongs the merit of carrying out some of the earliest determinations of the quantities by weight in which acids saturate bases and bases acids, and of arriving at the conception that those amounts of different bases which can saturate the same quantity of a particular acid are equivalent to each other.

He was thus led to conclude that chemistry is a branch of applied mathematics and to endeavour to trace a law according to which the quantities of different bases required to saturate a given acid formed an arithmetical, and the quantities of acids saturating a given base a geometrical, progression.

Berthelot, and many other chemists, from whose researches it results that glycerin is a trihydric alcohol indicated by the formula C 3 H 5 (OH) 3j the natural fats and oils, and the glycerides generally, being substances of the nature of compound esters formed from glycerin by the replacement of the hydrogen of the OH groups by the radicals of certain acids, called for that reason "fatty acids."

Thus in cows' butter, tributyrin, C 3 H 5 (O C 4 H 7 0) 3, and the analogous glycerides of other readily volatile acids closely resembling butyric acid, are present in small quantity; the production of these acids on saponification and distillation with dilute sulphuric acid is utilized as a test of a purity of butter as sold.

Another mode of separating the two acids is to convert them into calcium salts, which are then treated with a perfectly neutral solution of cupric chloride, soluble cupric citrate and calcium chloride being formed, while cupric tartrate remains undissolved.

The rationale of this treatment is not fully understood, but the action appears to consist in the separation or decomposition of the aromatic hydrocarbons, fatty and other acids, phenols, tarry bodies, &c., which lower the quality of the oil, the sulphuric acid removing some, while the caustic soda takes out the remainder, and neutralizes the acid which has been left in the oil.

In a scientific definition the compounds of fatty acids with basic metallic oxides, lime, magnesia, lead oxide, &c., should also be included under soap; but, as these compounds are insoluble in water, while the very essence of a soap in its industrial relations is solubility, it is better to speak of the insoluble compounds as " plasters, " limiting the name " soap " as the compounds of fatty acids with soda and potash.

Almost without exception potash soaps, even if made from the solid fatty acids, are " soft," and soda soaps, although made with fluid olein, are " hard "; but there are considerable variations according to the prevailing fatty acid in the compound.

As to the detergent action of a soap, Berzelius held that it was due to the free alkali liberated with water; but it is difficult to see why a solution which has just thrown off most of its fatty acids should be disposed to take up even a glyceride, and, moreover, on this theory, weak cold solutions, in which the hydrolysis is considerable, should be the best cleansers, whilst experience points to the use of hot concentrated solutions.

Resin soaps are compounds of soda or potash with the complex acids (chiefly abietic) of which coniferous resins consist.

As regards processes of manufacture soaps may be made by the direct combination of fatty acids, separated from oils, with alkaline solutions.

In the manufacture of stearin for candles, &c., the fatty matter is decomposed, and the liquid olein, separated from the solid fatty acids, is employed as an ingredient in soapmaking.

The process of manufacturing soaps by boiling fatty acids with caustic alkalis or sodium carbonate came into practice with the development of the manufacture of candles by saponifying fats, for it provided a means whereby the oleic acid, which is valueless for candle making, could be worked up. The combination is effected in open vats heated by a steam coil and provided with a stirring appliance; if soda ash be used it is necessary to guard against boiling over.

Lye still continues to be poured in till a sample tastes distinctly alkaline - a test which indicates that the whole of the fatty acids have been taken up by and combined with the alkali.

The more usual method is to take milling soap, neutralize it with sodium bicarbonate or a mixture of fatty acids, and, after perfuming, it is aerated by mixing the hot soap with air in a specially designed crutcher.

The first is carried out by saponifying the soap with acid in the heat when the fatty acids come to the surface.

With genuine soaps, however, it suffices to calculate the fatty acids as anhydrides and add to this the amount of alkalis, and estimate the water by difference.

They first invented and named the alembic for the purposes of distillation, analyzed the substances of the three kingdoms of nature, tried the distinction and affinities of alkalis and acids, and converted the poisonous minerals into soft and salutary remedies.

Acids have practically no action on the metal, but it is soluble in solutions of the alkaline hypochlorites.

It is insoluble in acids and decomposes when heated to a sufficiently high temperature.

The insoluble residue contains a mixture of two sulphides, one of which is converted into the sulphate by nitric acid, whilst the other (a crystalline solid) is insoluble in acids.

It forms very hard metallic-looking crystals, burns in oxygen and is not attacked by acids.

Notwithstanding the false idea which prompted the researches of the alchemists, many advances were made in descriptive chemistry, the metals and their salts receiving much attention, and several of our important acids being discovered.

Among the Arabian and later alchemists we find attempts made to collate compounds by specific properties, and it is to these writers that we are mainly indebted for such terms as "alkali," " sal," &c. The mineral acids, hydrochloric, nitric and sulphuric acids, and also aqua regia (a mixture of hydrochloric and nitric acids) were discovered, and the vitriols, alum, saltpetre, sal-ammoniac, ammonium carbonate, silver nitrate (lunar caustic) became better known.

The action of these acids on many metals was also studied; Glauber obtained zinc, stannic, arsenious and cuprous chlorides by dissolving the metals in hydrochloric acid, compounds hitherto obtained by heating the metals with corrosive sublimate, and consequently supposed to contain mercury.

Hydrobromic and hydriodic acids were investigated by Gay Lussac and Balard, while hydrofluoric acid received considerable attention at the hands of Gay Lussac, Thenard and Berzelius.

Gerland contributed to our knowledge of vanadyl salts and the vanadic acids.

A new and energetic spirit was introduced by Scheele; among other discoveries this gifted experimenter isolated and characterized many organic acids, and proved the general occurrence of glycerin (Olsiiss) in all oils and fats.

According to this theory a " chemical type " embraced compounds containing the same number of equivalents combined in a like manner and exhibiting similar properties; thus acetic and trichloracetic acids, aldehyde and chloral, marsh gas and chloroform are pairs of compounds referable to the same 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.

From similar investigations of valerianic acid he was led to conclude that fatty acids were oxygen compounds of the radicals hydrogen, methyl, ethyl, &c., combined with the double carbon equivalent C2.

Lactic acid and alanine were shown to be oxyand amino-propionic acids respectively; glycollic acid and glycocoll, oxyand amino-acetic acids; salicylic and benzamic acids, oxyand amino-benzoic acids.

It is necessary clearly to distinguish such compounds as the amino- (or amido-) acids and acid-amides; in the first case the amino group is substituted in the hydrocarbon residue, in the second it is substituted in the carboxyl group.

This compound is readily oxidized to benzoic acid, C 6 H 5 000H, the aromatic residue being unattacked; nitric and sulphuric acids produce nitro-toluenes, C6H4 CH3 N02j and toluene sulphonic acids, C 6 H 4 CH 3 SO 3 H; chlorination may result in the formation of derivatives substituted either in the aromatic nucleus or in the side chain; the former substitution occurs most readily, chlor-toluenes, C 6 H 4 CH 3 Cl, being formed, while the latter, which needs an elevation in temperature or other auxiliary, yields benzyl chloride, C 6 H 5 CH 2 C1, and benzal chloride, C 6 11 5 CHC1 2.

Thus in the tri-substitution derivatives six isomers, and no more, are possible when two of the substituents are alike; for instance, six diaminobenzoic acids, C 6 H 3 (NH 2) 2 000H, are known; when all are unlike ten isomers are possible; thus, ten oxytoluic acids, C 6 H 3 -CH 3.

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.

From meta-brombenzoicacid two nitrobrombenzoic ac i ds are obtained on direct nitration; elimination of the bromine atom and the reduction of the nitro to an amino group in these two acids results in the formation of the same ortho-aminobenzoic acid.

Hence the positions occupied by the nitro groups in the two different nitrobrombenzoic acids must be symmetrical with respect to the carboxyl group. In 1879, Hubner (Ann., 1 95, p. 4) proved the equivalence of the second pair, viz.

This substance readily yields ortho-oxybenzoic acid or salicylic acid, which on nitration yields two mononitro-oxybenzoic acids.

By eliminating the hydroxy groups in these acids the same nitrobenzoic acid is obtained, which yields on reduction an aminobenzoic acid different from the starting-out acid.

Thus potassium ortho-oxybenzoate is converted into the salt of para-oxybenzoic acid at 220 0; the three bromphenols, and also the brombenzenesulphonic acids, yield m-dioxybenzene or resorcin when fused with potash.

Such a series of typical compounds are the benzene dicarboxylic acids (phthalic acids), C 6 H 4 (000H) 2.

P. Griess (Ber., 1872, 5, p. 192; 18 74, 7, p. 1223) orientated the three diaminobenzenes or phenylene diamines by considering their preparation by the elimination of the carboxyl group in the six diaminobenzoic acids.

Experience has shown that such mono-derivatives as nitro compounds, sulphonic acids, carboxylic acids, aldehydes, and ketones yield as a general rule chiefly the meta-compounds, and this is independent of the nature of the second group introduced; on the other hand, benzene haloids, amino-, homologous-, and hydroxy-benzenes yield principally a mixture of the orthoand para-compounds.

For many years it had been known that a mixture of potassium chlorate and hydrochloric or sulphuric acids possessed strong.

It is probable that tetrahydro acids are first formed, which suffer rearrangement to orthoketone carboxylic acids.

These substances absorb water and become pimelic acids.

From this acid the 0 dihydro and the tetrahydro acids may be obtained, from both of which the hexahydro acid may be prepared.

From the fact that reduction products containing either one or two double linkages behave exactly as unsaturated aliphatic compounds, being readily reduced or oxidized, and combining with the halogen elements and haloid acids, it seems probable that in benzenoid compounds the fourth valencies are symmetrically distributed in such a manner as to induce a peculiar stability in the molecule.

It is well known that di-orthosubstituted benzoic acids are esterified with difficulty.

Of great importance is his introduction of vegetable juices (the so-called indicators, q.v.) to detect acids and bases.

Small portions should be successively tested with waterMilute hydrochloric acid, dilute nitric acid, strong hydrochloric acid, and a mixture of hydrochloric and nitric acids, first in the cold and then with warming.

There is no general procedure for these operations, and it is customary to test for the acids separately by special tests; these are given in the articles on the various acids.

The washing is continued until the filtrate is free from salts or acids.

The first class includes those substances which require no preliminary treatment, and comprises the amides and ammonium compounds, pyridines, quinolines, alkaloids, albumens and related bodies; the second class requires preliminary treatment and comprises, with few exceptions, the nitro-, nitroso-, azo-, diazoand amidoazo-compounds, hydrazines, derivatives of nitric and nitrous acids, and probably cyanogen compounds.

By actual observations it has been shown that ether, alcohol, many esters of the normal alcohols and fatty acids, benzene, and its halogen substitution products, have critical constants agreeing with this originally empirical law, due to Sydney Young and Thomas; acetic acid behaves abnormally, pointing to associated molecules at the critical point.

Recent researches have shown that the law originally proposed by Kopp - " That the specific volume of a liquid compound (molecular volume) at its boiling-point is equal to the sum of the specific volumes of its constituents (atomic volumes), and that every element has a definite atomic value in its compounds " - is by no means exact, for isomers have different specific volumes, and the volume for an increment of CH 2 in different homologous series is by no means constant; for example, the difference among the esters of the fatty acids is about 57, whereas for the aliphatic aldehydes it is 49.

Schroeder the silver salts of the fatty acids exhibit additive relations; an increase in the molecule of CH2 causes an increase in the molecular volume of about 15'3.

The same difference attends the introduction of the methyl group into many classes of compounds, for example, the paraffins, olefines, acetylenes, aromatic hydrocarbons, alcohols, aldehydes, ketones and esters, while a slightly lower value (157.1) is found in the case of the halogen compounds, nitriles, amines, acids, ethers, sulphides and nitro compounds.

Mention may be made of the phenomenon of halochromism, the name given to the power of colourless or faintly-coloured substances of combining with acids to form highly-coloured substances without the necessary production of a chromophoric group. The researches of Adolf von Baeyer and Villiger, Kehrmann, Kauffmann and others, show that this property is possessed by very many and varied substances.

It is resinified by the action of concentrated mineral acids.

Potassium persulphate oxidizes it in alkaline solution, the product on boiling with acids giving hydroquiirone carboxylic acid (German Patent 81,297).

When boiled with calcium chloride and ammonia, salicylic acid gives a precipitate of insoluble basic calcium salicylate, C 6 H 4 ‹ 0 2 i Ca, a reaction which serves to distinguish it from the isomeric metaand para-hydroxybenzoic acids.

Hydrolysis with baryta water gives acetic and salicylic acids.

Salicylic acid and salicin (q.v.) share the properties common to the group of aromatic acids, which, as a group, are antiseptic without being toxic to man - a property practically unique; are unstable in the body; are antipyretic and analgesic; and diminish the excretion of urea by the kidneys.

They are hydrolysed by dilute mineral acids yielding hydroxylamine and the parent aldehyde or ketone.

It behaves as a powerful reducing agent, and on hydrolysis with dilute mineral acids is decomposed into formaldehyde and hydroxylamine, together with some formic acid and ammonia, the amount of each product formed varying with temperature, time of reaction, amount of water present, &c. This latter reaction is probably due to some of the oxime existing in the form of the isomeric formamide HCO NH 2.

The silver salt is a bright yellow solid, soluble in dilute sulphuric and nitric acids, and may be crystallized from concentrated solutions of ammonia.

The calcium salt, CaN 2 O 2.4H 2 O, formed by the action of calcium chloride on the silver salt in the presence of a small quantity of nitric acid, is a lustrous crystalline powder, almost insoluble in water but readily soluble in dilute acids.

P For sulphonic acids containing nitrogen see Ammonia.

The oxide dissolves slowly in acids; it is not reduced by hydrogen and is infusible.

A remarkable change occurs when many albumins are boiled with water, or treated with certain acids, their solubility and general characters being entirely altered, and the fluid becoming coagulated.

Boiling with dilute mineral acids, or baryta water, decomposes albumins into carbon dioxide, ammonia and fatty aminoand other acids.

Albumins (as classified above) are soluble in water, dilute acids and alkalies, and in saturated neutral salt solutions; they are coagulated by heat.

The globulins are insoluble in water and in dilute acids, but soluble in alkalies and in neutral salt solutions; these solutions are coagulated on boiling.

The nucleo-albumins or phospho-globulins are insoluble in water and acids, but soluble in alkalies, and have an acid reaction.

Histones are a class of albumins soluble in water and acids, but essentially basic in character; hence they are precipitated by alkalies.

They give the biuret and xanthoproteic reactions, and form salts with both acids and bases.

Acids and moist heat induce similar changes.

In general they are white, loose powders, slightly soluble in cold water, more soluble in hot water; they are precipitated by mineral acids, but dissolve in an excess.

Other derivatives are haemin, haemochromogen and the haematinic acids.

Chemically they resemble the albumins, being split up by acids or ferments into albumoses, peptones and amino-acids, forming salts, and giving N =C6 1 The pyrimidin ring is numbered 2C "C5.

They are quite insoluble in water and in salt solutions, and difficultly soluble in dilute acids and alkalies.

The decomposition products are generally the same as with the general albumin; it gives the biuret reaction; forms salts with acids and alkalies, but is essentially acid in nature.

It is quite insoluble in water, dilute acids and alkalies.

Fibroin is insoluble in water, acids and alkalies; silk-glue resembles gelatin in its solubility, but it is less readily gelatinized.

Melanins obtained from tumours form black, shiny masses; they are insoluble in water, neutral salt solutions, dilute acids and in the common organic solvents.

Amino derivatives similarly result from thio-ureas and a-haloid ketones; the oxy derivatives from a-sulphocyanoketones by the action of caustic alkali; and the carboxylic acids from chloro-aceto-acetic ester, &c. and thioamides.

In batteries which use acids as the electrolyte, a film of hydrogen tends to be deposited on the copper or platinum electrode; but, to obtain a constant electromotive force, several means were soon devised of preventing the formation of the film.

It is possible to distinguish between double salts and salts of compound acids.

But when we pass to solutions of mineral salts and acids - to solutions of electrolytes in fact - we find that the observed values of the osmotic pressures and of the allied phenomena are greater than the normal values.

The affinities of acids have been compared in several ways.

Determinations have been made with calcium oxalate, CaC 2 04+H 2 0, which is easily decomposed by acids, oxalic acid and a soluble calcium salt being formed.

The affinities of acids relative to that of oxalic acid are thus found, so that the acids can be compared among themselves (column II.).

It is found that the influence of different acids on this action is proportional to their specific coefficients of affinity.

A better basis of comparison would be the ratio of the actual to the limiting conductivity, but since the conductivity of acids is chiefly due to the mobility of the hydrogen ions, its limiting value is nearly the same for all, and the general result of the comparison would be unchanged.

The mean values of k for other common acids were - formic, 0.0000214; acetic, o 0000180; monochloracetic, 0.0.0155; dichloracetic, 0.051; trichloracetic, 1.21; propionic, 0.0000134.

From these numbers we can, by help of the equation, calculate the conductivity of the acids for any dilution.

For acids its value is usually rather less than for salts at equivalent concentrations.

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.

The name is applied in commerce to a complex mixture of carbohydrates obtained by boiling starch with dilute mineral acids; in chemistry, it denotes, with the prefixes d, 1 and d+l (or i), the dextro-rotatory, laevo-rotatory and inactive forms of the definite chemical compound defined above.

On reduction glucose appears to yield the hexahydric alcohol d-sorbite, and on oxidation d-gluconic and d-saccharic acids.

Caoutchouc is not dissolved by water or alcohol, and is not affected except by the strongest acids.

Other applications depend on the strength of its resistance to acids.

Aqueous non-oxidizing acids generally have little or no action on lead in the absence of air.

It ignites when heated in air with the formation of the monoxide; dilute acids convert it into metallic lead and lead monoxide, the latter dissolving in the acid.

Its specific gravity is about 9; it is sparingly soluble in water, but readily dissolves in acids and molten alkalis.

This salt gives the corresponding chloride and fluoride with hydrochloric and hydrofluoric acids, and the phosphate, Pb(HP04)2, with phosphoric acid.

It is decomposed by acids into a mixture of lead monoxide and dioxide, and may thus be regarded as lead metaplumbate, PbPbO 3.

Acids decompose it into lead dioxide and monoxide, and the latter may or may not dissolve to form a salt; red lead may, therefore, be regarded as lead orthoplumbate, Pb2Pb04.

Lead fluoride, PbF2, is a white powder obtained by precipitating a lead salt with a soluble fluoride; it is sparingly soluble in water but readily dissolves in hydrochloric and nitric acids.

Solutions of lead salts (colourless in the absence of coloured acids) are characterized by their behaviour to hydrochloric acid, sulphuric acid and potassium chromate.

When heated with hydriodic acid and phosphorus it forms phenylacetic acid; whilst concentrated hydrobromic acid and hydrochloric acid at moderate temperatures convert it into phenylbromand phenylchlor-acetic acids.

Darzens (Comptes Rendus, 1904, 139, p. 1214) prepares esters of disubstituted glycidic acids, by condensing the corresponding ketone with monochloracetic ester, in the presence of sodium ethylate.

It burns on heating in air; and is scarcely attacked by hydrochloric or nitric acids, or by aqua regia; it is soluble in warm concentrated sulphuric acid.

It is unattacked by acids.

They are colourless solids which are readily soluble in water and possess the character of weak acids.

When strongly heated they decompose, forming fatty acids, nitrogen peroxide and nitrogen.

When heated with water and mineral acids, the nitrolic acids are completely decomposed, yielding fatty acids and nitrous oxide.

They discriminate between the red or erythro-salts, which are well crystallized, very explosive and unstable compounds, and which regenerate the colourless nitrolic acid on the addition of dilute mineral acids, and the leuco-salts, which are colourless salts obtained by warming the erythro-salts or by exposing them to direct sunlight.

It fires when heated in air, and dissolves in acids to form uranous salts.

These salts generally resemble the bichromates; they are yellow in colour, insoluble in water, soluble in acids, and decomposed by heat.

In 1858 he pointed out the isomorphism of the fluostannates and the fluosilicates, thus settling the then vexed question of the composition of silicic acid; and subsequently he studied the fluosalts of zirconium, boron, tungsten, &c., and prepared silicotungstic acid, one of the first examples of the complex inorganic acids.

It is a very weak base, salts being only formed with mineral acids, and these are dissociated by water.

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.

Metastannic acid is distinguished from orthostannic acid by its insolubility in nitric and sulphuric acids.

This acid, H 2 Sn0 3, is readily soluble in acids forming stannic salts, and in caustic potash and soda, with the formation of orthostannates.

Stannous salt solutions yield a brown precipitate of SnS with sulphuretted hydrogen, which is insoluble in cold dilute acids and in real sulphide of ammonium, (NH 4) 2 S; but the yellow, or the colourless reagent on addition of sulphur, dissolves the precipitate as SnS 2 salt.

Stannic salt solutions give a yellow precipitate of SnS 2 with sulphuretted hydrogen, which is insoluble in cold dilute acids but readily soluble in sulphide of ammonium, and is re-precipitated therefrom as SnS2 on acidification.

Under acids it yields the following reaction C48 H 60018 +H20 =2C16 141806+C10th40-1-C6H1.206.

The constitution of guncotton is a difficult matter to investigate, primarily on account of the very insoluble nature of cellulose itself, and also from the fact that comparatively slight variations in the concentration and temperature of the acids used produce considerable differences in the products.

Guncotton is made by immersing cleaned and dried cotton waste in a mixture of strong nitric and sulphuric acids.

Abel, the cotton is ground into a pulp, a process which greatly facilitates the complete removal of acids, &c. This pulp is finally drained, and is then either compressed,while still moist, into slabs or blocks when required for blasting purposes, or it is dried when required for the manufacture of propellants.

Dilute mineral acids have little or no action on guncotton.

The neutral fats are composed of fatty acids and glycerin.

From whatever cause the tissues become disorganized and undergo fatty degeneration, the fatty acids may become liberated and combine with the alkalies to form potash and soda soaps.

In recent practice some sulphin trioxide, or fuming sulphuric acid, is added, so that the mixture of acids contains less than I% of water.

The action is very rapid, and the product, which rises to the top of the acids, is separated and washed successively with cold and then tepid water, and finally with water made slightly alkaline with sodium carbonate or hydroxide, to remove all adhering or dissolved acids which would otherwise render the product very unstable.

Bernthsen (Ann., 1884, 224, p. 1) condensed diphenylamine with fatty acids, in the presence of zinc chloride.

These substances condense to form tetra-aminotriphenylmethane, which, on heating with acids, loses ammonia and yields diaminodihydrophenylacridine, from which benzoflavin is obtained by oxidation.

Water decomposes it into hydrochloric and silicic acids.

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.

The carbonates are decomposed by mineral acids, with formation of the corresponding salt of the acid, and liberation of carbon dioxide.

Aqua Regia, a mixture of nitric and hydrochloric acids, converts all metals (even gold, the "king of metals," whence the name) into chlorides, except only rhodium, iridium and ruthenium, which, when pure, are not attacked.

They are neutral to litmus and do not combine with dilute acids or bases; strong bases, such as lime and baryta, yield saccharates, whilst, under certain conditions, acids and acid anhydrides may yield esters.

Also (d +1) mannonic acid can be split into the d and 1 acids by fractional crystallization of the strychnine or brucine salts.

Thus Wohl prepared l-threose from l-xylose and l-erythrose from l-arabinose, and Ruff obtained d- and l-erythrose from d- and l-arabonic acids, the oxidation products of d- and l-arabinoses.

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.

Hence it follows that the " optical " formulae of the acids derived from two pentoses having the configuration given above will be C02H - 0 - C02H CO 2 H + 0 - C02H, and that consequently only one of the acids will be optically active.

On reduction it yields an inactive mixture of galactonic acids, some molecules being attacked at one end, as it were, and an equal number of others at the other.

It is oxidized by nitric acid to d-saccharic and mucic acids; and acetic anhydride gives an octa-acetate.

Styrolene is oxidized by nitric or chromic acids to benzoic acid; reduction gives ethylbenzene; hydrochloric and hydrobromic acids yield a-haloid ethylbenzenes, e.g.

Many derivatives are known, some of which exist in two structural forms, exhibiting geometrical isomerism after the mode of fumaric and maleic acids.

By heating the nitrate it is obtained as hemimorphous pyramids belonging to the hexagonal system; and by heating the chloride in a current of steam as hexagonal prisms. It is insoluble in water; it dissolves readily in all aqueous acids, with formation of salts.

To acids and to alkalis it behaves like the oxide, but dissolves more readily.

It dissolves in mineral acids, but is insoluble in acetic acid.

Graham's doctrine of polybasicity was extended to the organic acids.

Liebig also did much to further the hydrogen theory of acids.

The so-called "stearin" of candles is a mixture of stearic and palmitic acids.

The pure substances are best obtained by fusion of the corresponding toluene sulphonic acids with potash.

Numerous sulphonic acids of anthracene are known, a monosulphonic acid being obtained with dilute sulphuric acid, whilst concentrated sulphuric acid produces mixtures of the anthracene disulphonic acids.

It is insoluble in all acids, except in hot concentrated sulphuric, when finely powdered.

The ortho-body dissolves in cold dilute acids; the meta-body does not.

This salt is decomposed by water with the formation of a solution of alkali free of titanium, and a residue of an acid titanate, which is insoluble in water but soluble in cold 'aqueous mineral acids.

They are all strong bases, readily forming salts with the mineral acids and double salts with the chlorides of gold, platinum and mercury.

Aromatic Amines.-The aromatic amines in some respects resemble the aliphatic amines, since they form salts with acids, and double salts with platinum chloride, and they also distil without decomposition.

When heated with monobasic saturated acids and zinc chloride it yields acridines.

Nitric, hydrochloric and sulphuric acids, all more or less impure, were better studied; and many ethereal oils were discovered.

Instances of its application are found in the separation of orthoand para-nitrophenol, the o-compound distilling and the p- remaining behind; in the separation of aniline from the mixture obtained by reducing nitrobenzene; of the naphthols from the melts produced by fusing the naphthalene monosulphonic acids with potash; and of quinoline from the reaction between aniline, nitrobenzene, glycerin, and sulphuric acid (the product being first steam distilled to remove any aniline, nitrobenzene, or glycerin, then treated with alkali, and again steam distilled when quinoline comes over).

Again, anode reactions, such as are observed in the electrolysis of the fatty acids, may be utilized, as, for example, when the radical CH3C02 - deposited at the anode in the electrolysis of acetic acid - is dissociated, two of the groups react to give one molecule of ethane, C 2 H 6, and two of carbon dioxide.

Of the general characters of acids we may here notice that they dissolve alkaline substances, certain metals, &c., neutralize alkalies and redden many blue and violet vegetable colouring matters.

The ancients probably possessed little knowledge indeed of acids.

At about the same time Boyle investigated several acids; he established their general reddening of litmus, their solvent power of metals and basic substances, and the production of neutral bodies, or salts, with alkalies.

Theoretical conceptions were revived by Stahl, who held that acids were the fundamentals of all salts, and the erroneous idea that sulphuric acid was the principle of all acids.

The phlogistic theory of the processes of calcination and combustion necessitated the view that many acids, such as those produced by combustion, e.g.

This principle more or less prevailed until it was overthrown by Lavoisier's doctrine that oxygen was the acid-producing element; Lavoisier being led to this conclusion by the almost general observation that acids were produced when non-metallic elements were burnt.

The existence of acids not containing oxygen was, in itself, sufficient to overthrow this idea, but, although Berthollet had shown, in 1789, that sulphuretted hydrogen (or hydrosulphuric acid) contained no oxygen, Lavoisier's theory held its own until the researches of Davy, Gay-Lussac and Thenard on hydrochloric acid and chlorine, and of Gay-Lussac on hydrocyanic acid, established beyond all cavil that oxygen was not essential to acidic properties.

Liebig promoted his doctrine of polybasic acids.

This view, which was specially supported by Gay-Lussac and Leopold Gmelin and accepted by Berzelius, necessitated that all acids were monobasic. The untenability of this theory was proved by Thomas Graham's investigation of the phosphoric acids; for he then showed that the ortho- (ordinary), pyroand metaphosphoric acids contained respectively 3, 2 and I molecules of " basic water " (which were replaceable by metallic oxides) and one molecule of phosphoric oxide, P2 05.

Graham's work was developed by Liebig, who called into service many organic acids - citric, tartaric, cyanuric, comenic and meconic - and showed that these resembled phosphoric acid; and he established as the criterion of polybasicity the existence of compound salts with different metallic oxides.

In formulating these facts Liebig at first retained the dualistic conception of the structure of acids; but he shortly afterwards perceived that this view lacked generality since the halogen acids, which contained no oxygen but yet formed salts exactly similar in properties to those containing oxygen, could not be so regarded.

This and other reasons led to his rejection of the dualistic hypothesis and the adoption, on the ground of probability, and much more from convenience, of the tenet that " acids are particular compounds of hydrogen, in which the latter can be replaced by metals "; while, on the constitution of salts, he held that " neutral salts are those compounds of the same class in which the hydrogen is replaced by its equivalent in metal.

The substances which we at present term anhydrous acids (acid oxides) only become, for the most part, capable of forming salts with metallic oxides after the addition of water, or they are compounds which decompose these oxides at somewhat high temperatures."

Reference should be made to the articles Chemical Action, Thermochemistry and Solutions, for the theory of the strength or avidity of acids.

Oxy-acids are carboxylic acids which also contain a hydroxyl group; similarly we may have aldehyde-acids, ketone-acids, &c. Since the more important acids are treated under their own headings, or under substances closely allied to them, we shall here confine ourselves to general relations.

It is convenient to distinguish between aliphatic and aromatic acids; the first named being derived from open-chain hydrocarbons, the second from ringed hydrocarbon nuclei.

Aliphatic monobasic acids are further divided according to the nature of the parent hydrocarbon.

Dibasic acids of the paraffin series of hydrocarbons have the general formula C n H 2 (000H) 2 "; malonic and succinic acids are important members.

A list of the acids present in fats and oils is given in the article Oils.

Acids frequently result as oxidation products, being almost invariably formed in all cases of energetic oxidation.

There are certain reactions, however, in which oxidation can be successfully applied to the synthesis of acids.

An important oxidation synthesis of aromatic acids is from hydrocarbons with aliphatic side chains; thus toluene, or methylbenzene, yields benzoic acid, the xylenes, or dimethyl-benzene, yield methyl-benzoic acids and phthalic acids.

Ketones, secondary alcohols and tertiary alcohols yield a mixture of acids on oxidation.

We may also notice the disruption of unsaturated acids at the double linkage into a mixture of two acids, when fused with potash.

It is apparent that metallic salts of organic acids would, in aqueous solution, be ionized, the positive ion being the metal, and the negative ion the acid residue.

On treatment with zinc and alkyl iodides or with zinc alkyls they are converted into esters of hydroxy-dialkyl acetic acids.

It is only slightly soluble in water, but is readily soluble in acids and alkalis.

It dissolves most organic compounds, resins, hydrocarbons, fatty acids and many metallic salts, sometimes forming, in the latter case, crystalline compounds in which the ethyl alcohol plays a role similar to that of water of crystallization.

It is insoluble in hydrochloric, nitric and sulphuric acids, but dissolves in aqua regia - a mixture of hydrochloric and nitric acids - and when very finely divided in a heated mixture of strong sulphuric acid and a little nitric acid; dilution with water, however, precipitates the metal as a violet or brown powder from this solution.

Other metals which find application in the metallurgy of gold by virtue of their property of extracting the gold as an alloy are lead, which combines very readily when molten, and which can afterwards be separated by cupellation, and copper, which is separated from the gold by solution in acids or by electrolysis; molten lead also extracts gold from the copper-gold alloys.

Sulphur dioxide, generated by burning sulphur, is forced into the solution under pressure, where it interacts with any free chlorine present to form hydrochloric and sulphuric acids.

The a-naphthylamine sulphonic acids are used for the preparation of azo dyes, these dyes possessing the important property of dyeing unmordanted cotton.

Numerous sulphonic acids derived from 0-naphthylamine are known, the more important of which are the 2.8 or Badische, the 2.5 or Dahl, the 2.7 or S, and the 2.6 or Bronner acid.

Thus obtained it is a yellow powder, soluble in the mineral acids to form soluble salts, which are readily precipitated as basic salts when the solution is diluted.

It is best obtained by decomposing metallic tellurides with mineral acids.

Some tellurates exist in two forms, a colourless form soluble in water and acids, and a yellow form insoluble in water and acids.

It is unaffected by any acid or mixture of acids, but burns to the pentoxide when heated.

It is insoluble in all acids.

In modern chemistry alkali is a general term used for compounds which have the property of neutralizing acids, and is applied more particularly to the highly soluble hydrates of sodium and potassium and of the three rarer "alkali metals," caesium, rubidium and lithium, also to aqueous ammonia.

These enabled him to elucidate the true nature of soap; he was also able to discover the composition of stearin and olein, and to isolate stearic and oleic acids, the names of which were invented by him.

This fact explains the so-called "catalytic" action of acids and bases in decomposing such compounds as the esters.

Dioxyand tetraoxy-anthraquinones are obtained when meta-oxyand dimeta-dioxy-benzoic acids are heated with concentrated sulphuric acid.

Various sulphonic acids of anthraquinone are known, as well as oxy-derivatives, for the preparation and properties of which see Alizarin.

Filtration in the chemical laboratory is commonly effected by the aid of a special kind of unsized paper, which in the more expensive varieties is practically pure cellulose, impurities like feric oxide, alumina, lime, magnesia and silica having been removed by treatment with hydrochloric and hydrofluoric acids.

In the case of liquids containing strong acids or alkalis, which the paper cannot withstand, a plug of carefully purified asbestos or glass-wool (spun glass) is often employed, contained in a bulb blown as an enlargement on a narrow "filtertube."

After fusion, the mass is finely powdered and treated with cold dilute hydrochloric acid; and when action has finished, nitric and sulphuric acids are added, the precipitated barium sulphate removed, the liquid distilled and the osmium precipitated as sulphide.

In the massive state it is insoluble in all acids, but when freshly precipitated from solutions it dissolves in fuming nitric acid.

It is insoluble in acids and exists in several hydrated forms. The osmiates, corresponding to the unknown trioxide 0503, are red or green coloured salts; the solutions are only stable in the presence of excess of caustic alkali; on boiling an aqueous solution of the potassium salt it decomposes readily, forming a black precipitate of osmic acid, H20s04.

Mineral acids generally attack the crystallized metal very little even in the heat; aqua regia, however, dissolves it readily, and so does hydrofluoric acid.

Zirconium hydroxide, Zr(OH) 4, as thus obtained, is quite appreciably soluble in water and easily in mineral acids, with formation of zirconium salts, e.g.

But, if the hydroxide is precipitated in the heat, it demands concentrated acids for its solution.

Zirconia, like stannic and titanic oxides, unites not only with acids but also with basic oxides.

On long heating the syrup is partially converted into pyrophosphoric and metaphosphoric acids, but on adding water and boiling the ortho-acid is re-formed.

Metaphosphoric acid can be distinguished from the other two acids by its power of coagulating albumen, and by not being precipitated by mag nesium and ammonium chlorides in the presence of ammonia.

Being soluble in water containing carbonic acid or organic acids it may be readily removed in solution, and may thus furnish plants and animals with the phosphates required in their structures.

Meyerdahl obtained 4% of palmitic acid, 20% of jecoleic acid, C19H3602, and 20% of therapic acid, C 17 H 28 O 2; other investigators have recognized jecoric acid, C 18 H 30 O 2, asellic acid, C17H3202, and physetoleic acid, C16Hn02, but some uncertainty attends these last three acids.

Therapic and jecoleic acids apparently do not occur elsewhere in the animal kingdom, and it is probable that the therapeutic properties of the oil are associated with the presence of these acids, and not with the small amount of iodine present as was at one time supposed.

The salts produced by the action of ammonia on acids are known as the ammonium salts and all contain the compound radical ammonium (NH 4).

Their alkyl derivatives readily oxidize to pyrazine carboxylic acids.

Acids yield a sodium salt and free oxygen or hydrogen peroxide; with carbon dioxide it gives sodium carbonate and free oxygen; carbon monoxide gives the carbonate; whilst nitrous and nitric oxides give the nitrate.

It is purified by boiling with acids, to remove any mineral matter, and is then ignited for a long time in a current of chlorine in order to remove the last traces of hydrogen.

It may also be prepared by heating formic and oxalic acids (or their salts) with concentrated sulphuric acid (in the case of oxalic acid, an equal volume of carbon dioxide is produced); and by heating potassium ferrocyanide with a large excess of concentrated sulphuric acid, K 4 Fe(CN) 6 -i-6H2S04+6H20=2K2S04+FeS04+3(NH4)2S04+6C0.

It is a constituent of the minerals cerussite, malachite, azurite, spathic iron ore, calamine, strontianite, witherite, calcite aragonite, limestone, &c. It may be prepared by burning carbon in excess of air or oxygen, by the direct decomposition of many carbonates by heat, and by the decomposition of carbonates with mineral acids, M2C03+2HC1=2MCl-FH 2 O+CO 2.

For the salts of other sulphur acids, see Sulphur.

In the last years of his life he returned to the vegetable acids, and investigated citric, malic, oxalic and gallic acids.

Potash fusion decomposes it into benzoic and acetic acids.

For the oxy-cinnamic acids see Coumarin.

Sulphuric acid is now added to the liquid, and any alkaline sulphides and sulphites present are decomposed, while iodides and bromides are converted into sulphates, and hydriodic and hydrobromic acids are liberated and remain dissolved in the solution.

It is a powerful reducing agent, and is frequently employed for this purpose in organic chemistry; thus hydroxy acids are readily reduced on heating with the concentrated acid, and nitro compounds are reduced to amino compounds, &c. It is preferable to use the acid in the presence of amorphous phosphorus, for the iodine liberated during the reduction is then utilized in forming more hydriodic acid, and consequently the original amount of acid goes much further.

The anhydrous acid combines with hydrochloric, hydrobromic and hydriodic acids to form crystalline addition products, which are decomposed by water with the formation of the corresponding ammonium salt and formic acid.

The double cyanides formed by the solution of the cyanide of a heavy metal in a solution of potassium cyanide are decomposed by mineral acids with liberation of hydrocyanic acid and formation of the cyanide of the heavy metal.

It is insoluble in water and is not decomposed by acids.

It is insoluble in dilute acids.

The esters of the acid may be obtained by distilling a mixture of the sodium or potassium salts and the corresponding alcohol with hydrochloric or sulphuric acids.

In his earlier years he devoted himself to chemistry, both theoretical and applied, publishing papers on the preparation of gold and platinum, numerical relations between the atomic weights of analogous elements, the formation of aventurine glass, the manufacture of illuminating gas from wood, the preservation of oil-paintings, &c. The reaction known by his name for the detection of bile acids was published in 1844.

Real larch turpentine is a thick tenacious fluid, of a deep yellow colour, and nearly transparent; it does not harden by time; it contains 15% of the essential oil of turpentine, also resin, succinic, pinic and sylvic acids, and a bitter extractive matter.

Ostwald (ibid., 1900, 35, pp. 33, 204) has observed that on dissolving chromium in dilute acids, the rate of solution as measured by the evolution of gas is not continuous but periodic. It is largely made as ferro-chrome, an alloy containing about 60-70% of chromium, by reducing chromite in the electric furnace or by aluminium.

After ignition it becomes almost insoluble in acids, and on fusion with silicates it colours them green; consequently it is used as a pigment for colouring glass and china.

The bromide and iodide are formed in a similar manner by heating the metal in gaseous hydrobromic or hydriodic acids.

It dissolves iodine and absorbs chlorine, and is decomposed by water with formation of chromic and hydrochloric acids; it takes fire in contact with sulphur, ammonia, alcohol, &c., and explodes in contact with phosphorus; it also acts as a powerful oxidizing agent.

Investigation has shown that the change is due to the splitting off of sulphuric acid during the process, and that green-coloured chromsulphuric acids are formed thus - ii?

Several other complex chrom-sulphuric acids are known, e.g.

The resins which are obtained as natural exudations are in general mixtures of different, peculiar acids, named the resin acids, which dissolve in alkalis to form resin soaps, from which the resin acids are regenerated by treatment with acids.

Examples of resin acids are abietic (sylvic) acid, C19H2802, occurring in colophony, and pimaric acid, C20H3002, a constituent of gallipo resin.

It has the characteristic appearance of pure silk - a brilliant soft white body with a pearly lustre - insoluble in water, alcohol and ether, but it dissolves freely in concentrated alkaline solutions, mineral acids, strong acetic acid and in ammoniacal solution of oxide of copper.

Three acids of this empirical formula are known, viz.

Potash fusion converts it into acetic acid; nitric acid oxidizes it to acetic and oxalic acids; chromic acid mixture to acetaldehyde and acetic acid, and potassium permanganate to a0-dioxybutyric acid.

It is, however, more readily ob tained by boiling citraor meso-brompyrotartaric acids with alkalis.

It is rapidly dissolved by dilute acids, with the evolution of hydrogen and the formation of magnesium salts.

It is a non-volatile and almost infusible white powder, which slowly absorbs moisture and carbon dioxide from air, and is readily soluble in dilute acids.

The carbonate is not easily soluble in dilute acids, but is readily soluble in water containing carbon dioxide.

It is a white amorphous powder, readily soluble in acids.

The products formed by the action of the Grignard reagent with the various types of organic compounds are usually thrown out of solution in the form of crystalline precipitates or as thick oils, and are then decomposed by ice-cold dilute sulphuric or acetic acids, the magnesium being removed as a basic halide salt.

It was first prepared by Wilhelm Homberg (1652-1715) from borax, by the action of mineral acids, and was given the name sal sedativum Hombergi.

The same law prescribes conditions under which children between fourteen and eighteen years of age may be employed in the manufacture of white-lead, red-lead, paints, phosphorus, poisonous acids, tobacco or cigars, in mercantile establishments, stores, hotels, offices or in other places requiring protection to their health or safety; and it forbids the employment of boys under sixteen years of age or of girls under eighteen years of age in such factories or establishments more than ten hours a day (unless it be to prepare for a short day) or for more than fifty-eight hours to be chosen for the same term of service each voter shall vote for one only, and when three are to be chosen he shall vote for no more than two; candidates highest in vote shall be declared elected."

On the other hand, solution of mineral acids and salts conduct the current with chemical decomposition - they are called electrolytes.

Certain solvents, such as water, liquid ammonia or liquid hydrocyanic acid, possess the power of making some solutes, such as mineral salts and acids, when dissolved in them, conductors of electricity.

Characteristic yellow staining of the skin round the mouth from the formation of xanthoproteic acid serves to distinguish it from poisoning by other acids.

A large number of these acids, which are mostly benzene derivatives, have been isolated and more or less closely investigated.

These pigments primarily depend upon special acids contained in the thalli of lichens, and their presence may readily be detected by means of the reagents already noticed.

Zukal has considered that the lichen acids protect the lichen from the attacks of animals; the experiments of Zopf, however, have cast doubt on this; certainly lichens containing very bitter acids are eaten by mites though some of the acids appear to be poisonous to frogs.

He took the same course soon afterwards with four other papers, two of which - "On the quantity of acids, bases and salts in different varieties of salts" and "On a new and easy method of analysing sugar," contain his discovery, regarded by him as second in importance only to the atomic theory, that certain anhydrous salts when dissolved in water cause no increase in its volume, his inference being that the "salt enters into the pores of the water."

His most important achievement was to define "salts" - a term formerly used in the most loose and indeterminate way - as the compounds formed by the union of acids and bases, and further to distinguish between neutral, basic and acid salts.

To inorganic acids, except hydrochloric, it is highly resistant, ranking well with tin in this respect; but alkalis dissolve it quickly.

Organic acids such as vinegar, common salt, the natural ingredients of food, and the various extraneous substances used as food preservatives, alone or mixed together, dissolve traces of it if boiled for any length of time in a chemicallyclean vessel; but when aluminium utensils are submitted to the ordinary routine of the kitchen, being used to heat or cook milk, coffee, vegetables, meat and even fruit, and are also cleaned frequently in the usual fashion, no appreciable quantity of metal passes into the food.

This powder, provided that it has not been too' strongly ignited, is soluble in strong acids; by ignition it becomes denser and nearly as hard as corundum; it fuses in the oxyhydrogen flame or electric arc, and on cooling it assumes a crystalline form closely resembling the mineral species.

Both these soluble hydrates are readily coagulated by traces of a salt, acid or alkali; Crum's hydrate does not combine with dye-stuffs, neither is it soluble in excess of acid, while Graham's compound readily forms lakes, and readily dissolves when coagulated in acids.

It contains palmitic and several other fatty acids, among which there is one - ricinoleic acid - peculiar to itself.

On oxidation, the molecule is split at the carbonyl group and a mixture of acids is obtained.

Dilute nitric acid oxidizes it to acetic and oxalic acids, while potassium permanganate oxidizes it to acetone, carbon dioxide and oxalic acid.

Invisible to the microscope, but rendered visible by reagents, are glycogen, Mucor, Ascomycetes, yeast, &c. In addition to these cell-contents we have good indirect evidence of the existence of large series of other bodies, such as proteids, carbohydrates, organic acids, alkaloids, enzymes, &c. These must not be confounded with the numerous substances obtained by chemical analysis of masses of the fungus, as there is often no proof of the manner of occurrence of such bodies, though we may conclude with a good show of probability that some of them also exist preformed in the living cell.

Numerous di- and tri-sulphonic acids are known.

Numerous mono-, diand trisulphonic acids of a-naphthol are employed in the preparation of azo dyes.

The 0-naphthol sulphonic acids find extensive application in the colour industry.

Bamberger (Ber., 18 94, 27, p. 9 1 4) obtained the diazoic acids, R NH NO 2, substances which he had previously prepared by similarly oxidizing the diazonium salts, by dehydrating the nitrates of primary amines with acetic anhydride, and by the action of nitric anhydride on the primary amines.

Concentrated acids convert them into the isomeric nitro-amines, the - NO 2 group going into the nucleus in the orthoor paraposition to the amine nitrogen; this appears to indicate that the compounds are nitramines.

They are yellow crystalline solids, which do not unite with acids.

Halogen acids convert it into monohalogen fatty acids, and the halogens themselves convert it into dihalogen fatty acids.

It unites with aldehydes to form esters of ketonic acids, and with aniline yields anilido-acetic acid.

Cavendish, who showed that it was formed when various metals were acted upon by dilute sulphuric or hydrochloric acids.

It may be prepared by the electrolysis of acidulated water, by the decomposition of water by various metals or metallic hydrides, and by the action of many metals on acids or on bases.