Acid Sentence Examples

The acid, when distilled slowly, is decomposed and yields a and 0-angelica lactones.

Christ, it tastes like battery acid.

Lister for isolating a pure culture of lactic acid bacterium.

He scowled at the immediate burn and taste of acid.

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.

Other yeasts are stated to form sulphurous acid in must and wort.

The barium and magnesium salts of this acid are formed when baryta and magnesia are fused with cobalt sesquioxide.

Certain acid fermentations are of common occurrence.

Concentrated hydrochloric acid converts it into oxamide.

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

By heating a mixture of cobalt oxalate and sal-ammoniac in air, it is obtained in the form of minute hard octahedra, which are not magnetic, and are only soluble in concentrated sulphuric acid.

It dissolves easily in water, forming the hydrated chloride, CoC12.6H20, which may also be prepared by dissolving the hydroxide or carbonate in hydrochloric acid.

Cobalt fluoride, CoF 2.2H 2 0, is formed when cobalt carbonate is evaporated with an excess of aqueous hydrofluoric acid, separating in rose-red crystalline crusts.

Hot concentrated sulphuric acid also decomposes allantoin, with production of ammonia, and carbon monoxide and dioxide.

Acid oxidizing agents, however, completely destroy them.

Iridium sesquichloride, IrC1 31 is obtained when one of the corresponding double chlorides is heated with concentrated sulphuric acid, the mixture being then thrown into water.

It is a brown-black powder soluble in hydrochloric acid, chlorine being simultaneously liberated.

It is also obtained by heating para-chlorphenoldisulphonic acid with potassium hydroxide.

When warmed with baryta water it gives uvitic acid.

Thenard and is best obtained by heating a mixture of the trioxide and fluorspar with concentrated sulphuric acid.

A saturated solution of the gas, in water, is a colourless, oily, strongly fuming liquid which after a time decomposes, with separation of metaboric acid, leaving hydrofluoboric acid HF BF3 in solution.

Podophyllin is a resinous powder obtained by precipitating an alcoholic tincture of the rhizome by means of water acidulated with hydrochloric acid.

Alkalis decompose it into picro-podophyllic acid and picro-podophyllin, minute traces of both of which occur in a free state in the rhizome.

The acid is inert, but picro-podophyllin is the active principle.

The properties of podophyllin resin vary with the reaction of the tissue with which it is in contact; where this is acid the drug is inert, the picro-podophyllin being precipitated.

Their produce has gradually decreased since the 17th century, and is now unimportant, but sulphate of copper, iron pyrites, and some gold, silver, sulphur and sulphuric acid, and red ochre are also produced.

Sodium amalgam or zinc and hydrochloric acid reduce it to lactic acid, whilst hydriodic acid gives propionic acid.

It readily condenses with aromatic hydrocarbons in the presence of sulphuric acid.

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

It forms a well-crystallized hydrazone with phenylhydrazine; and a-nitroso propionic acid with hydroxylamine.

It is monobasic and yields salts which only crystallize with great difficulty; when liberated, from these salts by a mineral acid it forms a syrupy nonvolatile mass.

They form compounds with hydrochloric acid when this gas is passed into their ethereal solution; these compounds, however, are very unstable, being readily decomposed by water.

They readily decompose on heating, and are easily hydrolysed by alkalies; they possess a somewhat more acid character than.

After the vigorous reaction has ceased and all the sodium has been used up, the mass is thrown into dilute hydrochloric acid, when the soluble sodium salts go into solution, and the insoluble boron remains as a brown powder, which may by filtered off and dried.

The dark product obtained is washed with water, hydrochloric acid and hydrofluoric acid, and finally calcined again with the oxide or with borax, being protected from air during the operation by a layer of charcoal.

Heated with sulphuric acid and with nitric acid it is oxidized to boric acid, whilst on fusion with alkaline carbonates and hydroxides it gives a borate of the alkali metal.

Boron hydride has probably never been isolated in the pure condition; on heating boron trioxide with magnesium filings, a magnesium boride Mg 3 B 2 is obtained, and if this be decomposed with dilute hydrochloric acid a very evil-smelling gas, consisting of a mixture of hydrogen and boron hydride, is obtained.

It forms slightly coloured small crystals possessing a strong disagreeable smell, and is rapidly decomposed by water with the formation of boric acid and sulphuretted hydrogen.

A pentasulphide B2S5 is prepared, in an impure condition, by heating a solution of sulphur in carbon bisulphide with boron iodide, and forms a white crystalline powder which decomposes under the influence of water into sulphur, sulphuretted hydrogen and boric acid.

Boron trioxide B203 is the only known oxide of boron; and may be prepared by heating amorphous boron in oxygen, or better, by strongly igniting boric acid.

Sulphuric acid dissolves it, forming a deepred solution.

When heated with concentrated hydrochloric acid the amino group is replaced by the hydroxyl group and the phenolic eurhodols are produced.

A curious property is to be observed when a crystal of pharmacosiderite is placed in a solution of ammonia - in a few minutes the green colour changes throughout the whole crystal to red; on placing the red crystal in dilute hydrochloric acid the green colour is restored.

As early as 1866, tannic acid, gallic acid, wood spirit, acetic acid, essential oil and eucalyptol were produced from various species of eucalyptus, and researches made by Australian chemists, notably by Messrs.

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.

Brugnatelli, who found in 1798 that if silver be dissolved in nitric acid and the solution added to spirits of wine, a white, highly explosive powder was obtained.

The constitution of fulminic acid has been investigated by many experimenters, but apparently without definitive results.

The researches of Liebig (1823), Liebig and Gay-Lussac (1824), and of Liebig again in 1838 showed the acid to be isomeric with cyanic acid, and probably (Hcno) 2, since it gave mixed and acid salts.

The alkaloid is obtained from an aqueous extract of tobacco by distillation with slaked lime, the distillate being acidified with oxalic acid, concentrated to a syrup and decomposed by potash.

Hydriodic acid and phosphorus at high temperature give a dihydro-compound, whilst sodium and alcohol give hexaand octo-hydro derivatives.

With bromine in acetic acid solution at ordinary temperature, nicotine yields a perbromide, C10H10Br2N20 HBr 3, which with sulphur dioxide, followed by potash, gives dibromcotinine, C10H10Br2N20, from which cotinine, C10H12N20, is obtained by distillation over zinc dust.

This base is resolved into its active components by d-tartaric acid, l-nicotine-d-tartrate crystallizing out first.

The astringent principle is a peculiar kind of tannic acid, called by chemists quercitannic, which, yielding more stable compounds with gelatine than other forms, gives oak bark its high value to the tanner.

The cups are the most valuable portion of the valonia, abounding in tannic acid; immature acorns are sometimes exported under the name of "camatina."

The electromotive force of each cell is i 07 volts and the resistance 3 ohms. The Fuller bichromate battery consists of an outer jar containing a solution of bichromate of potash and sulphuric acid, in which a plate of hard carbon is immersed; in the jar there is also a porous pot containing dilute sulphuric acid and a small quantity (2 oz.) of mercury, in which stands a stout zinc rod.

Simultaneously Hermann, a German chemical manufacturer, discovered the new metal in a specimen of zinc oxide which had been thought to contain arsenic, since it gave a yellow precipitate, in acid solution, on the addition of sulphuretted hydrogen.

It can be purified by solution in hydrochloric acid and subsequent precipitation by metallic zinc.

Cadmium sulphate, CdSO 4, is known in several hydrated forms; being deposited, on spontaneous evaporation of a concentrated aqueous solution, in the form of large monosymmetric crystals of composition 3CdSO 4.8H 2 O, whilst a boiling saturated solution, to which concentrated sulphuric acid has been added, deposits crystals of composition CdSO 4 4H 2 0.

Cadmium sulphide, CdS, occurs naturally as greenockite (q.v.), and can be artificially prepared by passing sulphuretted hydrogen through acid solutions of soluble cadmium salts, when it is precipitated as a pale yellow amorphous solid.

Cadmium nitrate, Cd(N03)2.4H20, is a deliquescent salt, which may be obtained by dissolving either the metal, or its oxide or carbonate in dilute nitric acid.

Considerable trade is done in agro di limone or lemon extract, which forms the basis of citric acid.

Boracic acid is chiefly found near Volterra, where there is also a little rock salt, but the main supply is obtained by evaporation.

The more important of those in use to-day are carbolic acid, the perchloride and biniodide of mercury, iodoform, formalin, salicylic acid, &c. Carbolic acid is germicidal in strong solution, inhibitory in weaker ones.

The so-called "pure" acid is applied to infected living tissues, especially to tuberculous sinuses or wounds, after scraping them, in order to destroy any part of the tuberculous material still remaining.

The aromatic and irritating fumes emitted by burning amber are mainly due to this acid.

Burmite and simetite agree also in being destitute of succinic acid.

Berthollet's theoretical views regarding the composition of the metallic oxides, and he also showed Berthollet's "zoonic acid" to be impure acetic acid (1802); but Berthollet (q.v.), so far from resenting these corrections from a younger man, invited him to become a member of the Societe d'Arcueil.

His researches on sebacic acid (1802) and on bile (1807), and his discovery of peroxide of hydrogen (1818) also deserve mention.

The difference between these two latter substances was first pointed out by Cronstedt, and in 1778 C. Scheele prepared molybdic acid from the sulphide.

It is soluble in dilute nitric acid, and in concentrated sulphuric acid; in the XVIII.

Molybdenum sesquioxide, Mo 2 O 3, a black mass insoluble in acids, is formed by heating the corresponding hydroxide in vacuo, or by digesting the trioxide with zinc and hydrochloric acid.

It forms quadratic prisms, having a violet reflex and insoluble in boiling hydrochloric acid.

Molybdenum trioxide, Mo03, is prepared by oxidizing the metal or the sulphide by heating them in air, or with nitric acid.

It sublimes in small rhombic tables or needles, and is slightly soluble in cold water, the solution possessing an acid reaction.

Several hydrated forms of the oxide are known, and a colloidal variety may be obtained by the dialysis of a strong hydrochloric acid solution of sodium molybdate.

The molybdates may be recognized by the fact that they give a white precipitate on the addition of hydrochloric or nitric acids to their solutions, and that with reducing agents (zinc and sulphuric acid) they give generally a blue coloration which turns to a green and finally to a brown colour.

It is a yellow amorphous powder which is soluble in dilute alkalis, the solution on acidification giving an hydroxide, C1 4 Mo 3 (OH) 2, which is soluble in nitric acid, and does not give a reaction with silver nitrate.

It is easily soluble in hot nitric acid.

Molybdenum trisulphide, MoS3, is obtained by saturating a solution of an alkaline molybdate with sulphuretted hydrogen and adding a mineral acid.

The sharp, broken end penetrates the skin, and into the slight wound thus formed the formic acid contained by the hair is injected.

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.

In both these cases the stimulation is followed, not only by movement, but by the secretion of an acid liquid containing a digestive juice, by virtue of which the insect is digested after being killed.

Ustilago, and filling a greenhouse with hydrocyanic acid gas when young insects are commencing their ravages, e.g.

Brilliantly colored spots and patches follow the action of acid fumes on the vegetation near towns and factories, and such particoloured leaves often present striking resemblance to autumn foliage.

This has a strong attraction for basic aniline dyes, and can usually be distinguished from other parts of the cell which are more easily colored by acid anilines.

Cellulose has an affinity for acid stains, pectic substances for basic stains.

In the yeast cell the nucleus is represented by a homogenous granule, probably of a nucleolar nature, surrounded and perhaps to some extent impregnated by chromatin and closely connected with a vacuole which often has chromatin at its periphery, and contains one or more volutin granules which appear to consist of nucleic acid in combination with an unknown base.

This is not by the supply of food alone, but also by the withdrawal of carbonic acid from the atmosphere, by which vegetation maintains the composition of the air in a state fit for the support of animal life.

The solution is then acidified, and the phenols are'liberated and form an oily layer on the surface of the acid.

The hydrogen of the hydroxyl group in phenol can be replaced by metals, by alkyl groups and by acid radicals.

They are not decomposed by boiling alkalis, but on heating with hydriodic acid they split into their components.

Nitro-phenols are readily obtained by the action of nitric acid on phenol.

By the action of dilute nitric acid; orthoand para-nitrophenols are obtained, the ortho-compound being separated from the para-compound by distillation in a current of steam.

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

The mixture is then cooled, acidified by means of sulphuric acid, and titrated with decinormal sodium thiosulphate solution.

Carbolic acid is an efficient parasiticide, and is largely used in destroying the fungus of ringworm and of the skin disease known as pityriasis versicolor.

A piece of cotton wool soaked in strong carbolic acid will relieve the pain of dental caries, but is useless in other forms of toothache.

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.

In all cases of carbolic acid poisoning the nervous influence is seen.

If it be absorbed from a surgical dressing there are no irritant symptoms, but when the acid is swallowed in concentrated form, symptoms of gastro-intestinal irritation occur.

The breathing becomes shallow, the drug killing, like nearly all neurotic poisons (alcohol, morphia, prussic acid, &c.), by paralysis of the respiratory centre, and the patient dying in a state of coma.

Carbolic acid and sulphates combine in the blood to form sulpho-carbolates, which are innocuous.

The symptoms of nerve-poisoning are due to the carbolic acid (or its salts) which circulate in the blood after all the sulphates in the blood have been used up in the formation of sulpho-carbolates (hence, during administration of carbolic acid, the urine should frequently be tested for the presence of free sulphates; as long as these occur in the urine, they are present in the blood and there is no danger).

If the acid has been swallowed, wash out the stomach and give chalk, the carbolate of calcium being insoluble.

Coprolite is reduced to powder by powerful mills of peculiar construction, furnished with granite and buhrstones, before being treated with concentrated sulphuric acid.

The acid renders it available as a manure by converting the calcium phosphate, Ca 3 P 2 O 8, that it contains into the soluble monocalcium salt, CaH 4 P 2 O 8, or "superphosphate."

Two oxides of germanium are known, the dioxide, GeO2, being obtained by roasting the sulphide and treatment with nitric acid.

It is a white powder, very slightly soluble in water, and possesses acid properties.

If excess of a mineral acid be added to a solution of an alkaline thiogermanate a white precipitate of germanium disulphide, GeS2, is obtained.

It can also be obtained by passing sulphuretted hydrogen through a solution of the dioxide in hydrochloric acid.

The germanium salts are most readily recognized by the white precipitate of the disulphide, formed in acid solutions, on passing sulphuretted hydrogen.

The mixed solution of poiysulphides and thiosulphate of calcium thus produced is clarified, diluted largely, and then mixed with enough of pure dilute hydrochloric acid to produce a feebly alkaline mixture when sulphur is precipitated.

The addition of more acid would produce an additional supply of sulphur (by the action of the H2S203 on the dissolved H 2 S); but this thiosulphate sulphur is yellow and compact, while the polysulphide part has the desired qualities, forming an extremely fine, almost white, powder.

To obtain pure sulphuretted hydrogen the method generally adopted consists in decomposing precipitated antimony sulphide with concentrated hydrochloric acid.

It is moderately soluble in water, the solution possessing a faintly acid reaction.

It is prepared on the industrial scale for the manufacture of sulphuric acid, for the preparation of sodium sulphate by the Hargreaves process, and for use as a bleaching-disinfecting agent and as a preservative.

The solution of the gas in water is used under the name of sulphurous acid.

The free acid has not been isolated, since on evaporation the solution gradually loses sulphur dioxide.

This solution possesses reducing properties,and gradually oxidizes to sulphuric acid on exposure.

Since the free acid would be dibasic, two series of salts exist, namely, the neutral and acid salts.

The acid salts have a neutral or slightly acid reaction.

Sulphurous acid may have either of the constitutions

There are various haloid derivatives of sulphurous acid.

When perfectly dry this oxide has no caustic properties; it combines rapidly, however, with water to form sulphuric acid, with the development of much heat.

It combines directly with concentrated sulphuric acid to form pyrosulphuric acid, H 2 S 2 0 7.

Fluorsulphonic acid, SO 2 F OH, is a mobile liquid obtained by the action of an excess of hydrofluoric acid on well-cooled sulphur trioxide.

A solution of the free acid may be prepared by adding oxalic acid to the solution of the sodium salt.

Although this acid appears to be derived from an oxide S203, it is not certain that the known sesquioxide is its anhydride.

The salts of the acid, however, are stable, the sodium salt in particular being largely used for photographic purposes under the name of "hypo."

The acid is considered to possess the structure 0 2 S(SH) (OH), since sodium thiosulphate reacts with ethyl bromide to give sodium ethyl thiosulphate, which on treatment with barium chloride gives presumably barium ethyl thiosulphate.

A solution of the free acid may be obtained by decomposing the barium salt with dilute sulphuric acid and concentrating the solution in vacuo until it attains a density of about 1.35 (approximately), further concentration leading to its decomposition into sulphur dioxide and sulphuric acid.

The dithionates are all soluble in water and when boiled with hydrochloric acid decompose with evolution of sulphur dioxide and formation of a sulphate.

The free acid is obtained (in dilute aqueous solution) by the addition of dilute sulphuric acid to an aqueous solution of the barium salt.

It is only stable in dilute aqueous solution, for on concentration the acid decomposes with formation of sulphuric acid, sulphur dioxide and sulphur.

The aqueous solution of the acid is fairly stable at ordinary temperatures.

Hexathionic acid, H 2 S 6 0 6, is probably present in the mother liquors from which potassium pentathionate is prepared.

The fouling of the air that results from the steam-engine, owing to the production of carbonic acid gas and of sulphurous fumes and aqueous vapour, is well known, and its use is now practically abandoned for underground working.

The residue is dissolved in alcohol and to the cold saturated solution a cold alcoholic solution of picric acid is added.

Hess, from his work, arrived at the converse conclusion, that when a series of bases were used to neutralize a given amount of an acid, the heat of neutralization was always the same.

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.

For example, when metallic zinc is dissolved in dilute sulphuric acid with production of zinc sulphate (in solution) and hydrogen gas, a definite quantity of heat is produced for a given amount of zinc dissolved, provided that the excess of energy in the initial system appears entirely as heat.

Thus if concentrated instead of dilute sulphuric acid acts upon zinc, the action takes place to a great extent not according to the equation given above, but according to the equation Zn +2H 2 SO 4 = ZnS04+S02+2 H20, sulphur dioxide and water being produced instead of hydrogen.

Thus by transposition we may write the last equation as follows 2HI =H2+12+12200 cal., and thus express that hydriodic acid when decomposed into its elements evolves 12200 cal.

Amongst endothermic compounds may be noted hydriodic acid, HI, acetylene, C 2 H 2, nitrous oxide, N 2 O, nitric oxide, NO, azoimide, N 3 H, nitrogen trichloride, NC1 3.

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.

It was at one time thought that the greater the heat of neutralization of an acid with a given base, the greater was the strength of the acid.

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.

Besides the petroleum refineries the town possesses oil-works (for fuel), flour-mills, sulphuric acid works and tobacco factories.

It is obtainable from most natural fatty bodies by the action of alkalis and similar reagents, whereby the fats are decomposed, water being taken up, and glycerin being formed together with the alkaline salt of some particular acid (varying with the nature of the fat).

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.

Some other glycerides isolated from natural sources are analogous in composition to tristearin, but with this difference, that the three radicals which replace hydrogen in glycerin are not all identical; thus kephalin, myelin and lecithin are glycerides in which two hydrogens are replaced by fatty acid radicals, and the third by a complex phosphoric acid derivative.

In the Glatz process the lye is treated with a little milk of lime, the liquid then neutralized with hydrochloric acid, and the liquid filtered.

Glycerin is also employed in the manufacture of formic acid.

Next he sought to prepare the inactive form of the acid by artificial means; and after great and long-continued labour he succeeded, and was led to the commencement of his classical researches on fermentation, by the observation that when the inactive acid was placed in contact with a special form of mould (Penicillium glaucum) the right-handed acid alone was destroyed, the left-handed variety remained unchanged.

In systematic chemistry, sodium hyposulphite is a salt of hyposulphurous acid, to which Schutzenberger gave the formula H 2 S0 2, but which Bernthsen showed to be H 2 S 2 0 4.

Nitrate of soda, Peruvian guano and superphosphate of lime in the form of bones dissolved by sulphuric acid were now added to the list of manures, and the practice of analysing soils became more general.

Of phosphoric acid, the cereal crops take up as much as, or more than, any other crops of the rotation, excepting clover; and the greater portion thus taken up is lost to the farm in the saleable product - the grain.

Of potash, each of the rotation crops takes up very much more than of phosphoric acid.

But much less potash than phosphoric acid is exported in the cereal grains, much more being retained in the straw, whilst the other products of the rotation - the root and leguminous crops - which are also supposed to be retained on the farm, contain very much more potash than the cereals, and comparatively little of it is exported in meat and milk.

Thus the whole of the crops of rotation take up very much more of potash than of phosphoric acid, whilst probably even less of it is ultimately lost to the land.

The nitric acid is most likely taken up chiefly as nitrate of lime, but probably as nitrate of potash also, and it is significant that the high nitrogen-yielding clover takes up, or at least retains, very little soda.

The chief interest of the place centres in its brine springs which are largely impregnated with carbonic acid gas and oxide of iron, and are efficacious in chronic catarrh of the respiratory organs, in liver and stomach disorders and women's diseases.

Salivary glands are present, and in some carnivorous forms (Dolium) these secrete free sulphuric acid (as much as 2% is present in the secretion), which assists the animal in boring holes by means of its FIG.

The orthoschists are white mica-schists produced by the shearing of acid rocks, such as felsite and porphyry.

The food passing into the crop is there acted on by the saliva and also by an acid gastric juice which passes forwards from the stomach through the proventriculus.

Dessaignes, who obtained it by oxidizing malic acid (Ann., 1858, 107, p. 251).

Malonic acid, as well as its esters, is characterized by the large number of condensation products it can form.

Many salts of the acid are known and, with the exception of those of the alkali metals, they are difficultly soluble in water.

Many esters of malonic acid have been prepared, the most important being the diethyl ester (malonic ester), CH 2 (000C 2 H 5) 2, which is obtained by dissolving monochloracetic acid in water, neutralizing the solution with potassium carbonate, and then adding potassium cyanide and warming the mixture until the reaction begins.

The mass is then covered with two-thirds of its weight of alcohol, and saturated with hydrochloric acid gas.

The half nitrile of malonic acid is cyanacetic acid, CN CH 2 COOH, which, in the form of its ester, may be obtained by the action of a solution of potassium cyanide on monochloracetic acid.

The solution obtained is neutralized, concentrated on the water-bath, acidified by sulphuric acid and extracted with ether.

The true nitrile of malonic acid is methylene cyanide, CH 2 (CN) 2, which is obtained by distilling a mixture of cyanacetamide and phosphorus pentoxide.

Thus by heating spirits of salt he obtained "marine acid air" (hydrochloric acid gas), and he was able to collect it because he happened to use mercury, instead of water, in his pneumatic trough.

Then he treated oil of vitriol in the same way, but got nothing until by accident he dropped some mercury into the liquid, when "vitriolic acid air" (sulphur dioxide) was evolved.

Scheele had done, and because he was employing a glass vessel he got "fluor acid air" (silicon fluoride).

Heating spirits of hartshorn, he was able to collect "alkaline air" (gaseous ammonia), again because he was using mercury in his pneumatic trough; then, trying what would happen if he passed electric sparks through the gas, he decomposed it into nitrogen and hydrogen, and "having a notion" that mixed with hydrochloric acid gas it would produce a "neutral air," perhaps much the same as common air, he synthesized sal ammoniac. Dephlogisticated air (oxygen) he prepared in August 1774 by heating red oxide of mercury with a burning-glass, and he found that in it a candle burnt with a remarkably vigorous flame and mice lived well.

Using average prices paid for nitrogen, phosphoric acid and potash when bought in large quantities and in good forms, these ingredients, in a ton of cotton seed, amount to $9.00 worth of fertilizing material.

The hulls thus burned produced an ash containing an average of 9% of phosphoric acid and 24% of potash - a very valuable fertilizer in itself, and one eagerly sought by growers of tobacco and vegetables.

The acid is thus obtained in colourless rhombic prisms of the composition C 6 H 8 0 7 +H 2 0.

Crystals of a different form are deposited from a strong boiling solution of the acid.

About 20 gallons of lemon juice should yield about 1 0 lb of crystallized citric acid.

The acid may also be prepared from the juice of unripe gooseberries.

Glycerin when treated with hydrochloric acid gives propenyl dichlorhydrin, which may be oxidized to s-dichloracetone.

This compound combines with hydrocyanic acid to form a nitrile which hydrolyses to dichlorhydroxy iso-butyric acid.

Potassium cyanide reacts with this acid to form the corresponding dinitrile, which is converted by hydrochloric acid into citric acid.

This series of operations proves the constitution of the acid.

Held synthesized the acid from ethyl chlor-acetoacetate (from chlorine and acetoacetic ester) by heating with potassium cyanide and saponifying the resulting nitrile.

The acetone dicarboxylic acid, CO(CH 2 CO 2 H) 2, so obtained combines with hydrocyanic acid, and this product yields citric acid on hydrolysis.

Citric acid has an agreeable sour taste.

A higher temperature decomposes this body into carbon dioxide and itaconic acid, C 5 H 6 0 4, which, again, by the expulsion of a molecule of water, yields citraconic anhydride, C 5 H 4 0 3.

It is a strong acid, and dissolved in water decomposes carbonates and attacks iron and zinc.

Citric acid, being tribasic, forms either acid monometallic, acid dimetallic or neutral trimetallic salts; thus, mono-, diand tri-potassium and sodium citrates are known.

On warming citric acid with an excess of lime-water a precipitate of calcium citrate is obtained which is redissolved as the liquid cools.

The impurities occasionally present in commercial citric acid are salts of potassium and sodium, traces of iron, lead and copper derived from the vessels used for its evaporation and crystallization, and free sulphuric, tartaric and even oxalic acid.

Tartaric acid, which is sometimes present in large quantities as an adulterant in commercial citric acid, may be detected in the presence of the latter, by the production of a precipitate of acid potassium tartrate when potassium acetate is added to a cold solution.

Citric acid is also distinguished from tartaric acid by the fact that an ammonia solution of silver tartrate produces a brilliant silver mirror when boiled, whereas silver citrate is reduced only after prolonged ebullition.

Citric acid is used in calico printing, also in the preparation of effervescing draughts, as a refrigerant and sialogogue, and occasionally as an antiscorbutic, instead of fresh lemon juice.

It is found that transparent oils under the influence of light absorb oxygen, becoming deeper in colour and opalescent, while strong acidity and a penetrating odour are developed, these changes being due to the formation of various acid and phenylated compounds, which are also occasionally found in fresh oils.

The distillates obtained are usually purified by treatment, successively, with sulphuric acid and solution of caustic soda, followed by washing with water.

The products obtained by the distillation of petroleum are not in a marketable condition, but require chemical treatment to remove acid and other bodies which impart a dark colour as well as an unpleasant odour to the liquid, and in the case of lamp-oils, reduce the power of rising in the wick by capillary attraction.

Eichler, of Baku, is stated to have been the first to introduce, in Russia, the use of sulphuric acid, followed by that of soda lye, and his process is in universal use at the present time.

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.

This treatment with acid and alkali is usually effected by agitation with compressed air.

Geoffroy in 1741 pointed out that the fat or oil recovered from a soap solution by neutralization with a mineral acid differs from the original fatty substance by dissolving readily in alcohol, which is not the case with ordinary fats and oils.

These discoveries of Geoffroy and Scheele formed the basis of Chevreul's researches by which he established the constitution of oils and the true nature of soap. In the article Oils it is pointed out that all fatty oils and fats are mixtures of glycerides, that is, of bodies related to the alcohol glycerin C 3H5(OH)3 i and some fatty acid such as palmitic acid (C 16 H 31 0 2)H.

The corresponding decomposition of a glyceride into an acid and glycerin takes place when the glyceride is distilled in superheated steam, or by boiling in water mixed with a suitable proportion of caustic potash or soda.

But in this case the fatty acid unites with the alkali into its potash or soda salt, forming a soap C3H5(C16H3102)3+3NaOH =3NaC16H3102+C,H5(OH) 3 Palmitin.

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.

Soap when dissolved in a large amount of water suffers hydrolysis, with formation of a precipitate of acid salt and a solution containing free alkali.

Chevreul found that a neutral salt soap hydrolysed to an acid salt, free alkali, and a small amount of fatty acid.

The extent to which a soap is hydrolysed depends upon the acid and on the concentration of the solution; it is also affected by the presence of metallic salts, e.g.

The processes of soap manufacture may be classified (a) according to the temperatures employed into (I) cold processes and (2) boiling processes, or (b) according to the nature of the starting material - acid or oil and fat - and the relative amount of alkali, into (1) direct saturation of the fatty acid with alkali, (2) treating the fat with a definite amount of alkali with no removal of unused lye, (3) treating the fat with an indefinite amount of alkali, also with no separation of unused lye, (4) treating the fat with an indefinite amount of alkali with separation of waste lye.

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.

Among the principal varieties are those which contain carbolic acid and other ingredients of coal tar, salicylic acid, petroleum, borax, camphor, iodine, mercurial salts, sulphur and tannin.

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

The cake on weighing gives the free acid.

The total alkali is determined by incinerating a weighed sample in a platinum dish, dissolving the residue in water, filtering and titrating the filtrate with standard acid.

Carbon bisulphide slowly oxidizes on exposure to air, but by the action of potassium permanganate or chromic acid it is readily oxidized to carbon dioxide and sulphuric acid.

These are washed with ammonium chloride until the filtrate is colourless, ignited, fused with caustic potash and nitre, the melt dissolved in water and nitric acid added to the solution until the colour of potassium ruthenate disappears.

Ruthenium in bulk resembles platinum in its general appearance, and has been obtained crystalline by heating an alloy of ruthenium and tin in a current of hydrochloric acid gas.

The peroxide, Ru04, is formed when a solution of potassium ruthenate is decomposed by chlorine, or by oxidizing ruthenium compounds with potassium chlorate and hydrochloric acid, or with potassium permanganate and sulphuric acid.

Ruthenium sulphides are obtained when the metal is warmed with pyrites and some borax, and the fused mass treated with hydrochloric acid first in the cold and then hot.

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.

Ruthenium sulphate, Ru(S04)2, as obtained by oxidizing the sulphide, is an orange-yellow mass which is deliquescent and dissolves in water, the solution possessing a strongly acid reaction.

In addition to its brilliance, vermilion is a pigment of great intensity and durability, remaining unaffected by acid fumes.

It is soluble in water and possesses an odour resembling that of acetic acid.

Exposure to sunlight converts it into trimesic acid (benzene-1.3.5-tricarboxylic acid).

Its solution in concentrated sulphuric acid is of a yellow colour and shows a marked blue fluorescence.

When fused with caustic potash it yields phenol and salicylic acid.

All four mono-hydroxyxanthones are known, and are prepared by heating salicylic acid with either resorcin, pyrocatechin or hydroquinone; they are yellow crystalline solids, which act as dyestuffs.

The former experiment had been performed by Scheele and Priestley, who had named the gas " phlogisticated air "; Lavoisier subsequently named it oxygen, regarding it as the " acid producer " (OE, sour).

For example, one volume of oxygen combined with two of hydrogen to form two volumes of steam, three volumes of hydrogen combined with one of nitrogen to give two volumes of ammonia, one volume of hydrogen combined with one of chlorine to give two volumes of hydrochloric acid.

For example, positive iron combined with negative oxygen to form positive ferrous oxide; positive sulphur combined with negative oxygen to form negative sulphuric acid; positive ferrous oxide combined with negative sulphuric acid to form neutral ferrous sulphate.

An acid (q.v.) is a compound of hydrogen, which element can be replaced by metals, the hydrogen being liberated, giving substances named salts.

An alkali or base is a substance which neutralizes an acid with the production of salts but with no evolution of hydrogen.

If an acid contains oxygen it is termed an oxyacid.

If one acid be known its name is formed by the termination -ic, e.g.

An acid is said to be monobasic, dibasic, tribasic, &c., according to the number of replaceable hydrogen atoms; thus HNO 3 is monobasic, sulphuric acid H 2 SO 4 dibasic, phosphoric acid H 3 PO 4 tribasic.

An acid terminating in -ous forms a salt ending in -ite, and an oxyacid ending in -ic forms a salt ending in -ate.

An acid salt is one in which the whole amount of hydrogen has not been replaced by metal; a normal salt is one in which all the hydrogen has been replaced; and a basic salt is one in which part of the acid of the normal salt has been replaced by oxygen.

The distribution of weight in chemical change is readily expressed in the form of equations by the aid of these symbols; the equation 2HC1+Zn =ZnCl2+H2, for example, is to be read as meaning that from 73 parts of hydrochloric acid and 65 parts of zinc, 136 parts of zinc chloride and 2 parts of hydrogen are produced.

When this oxide is brought into contact with water it combines with it forming sulphuric acid, H2S04.

For instance, sulphuric acid is usually represented by the formula S0 2 (OH) 2, which indicates that it may be regarded as a compound of the group SO 2 with twice the group OH.

Thus, in the production of hydrochloric acid from hydrogen and chlorine 22,000 calories are developed; in the production of hydrobromic acid from hydrogen and bromine, however, only 8440 caloriesare developed; and in the formation of hydriodic acid from hydrogen and iodine 6040 calories are absorbed.

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.

In the formation of gaseous hydrobromic acid from liquid bromine and gaseous hydrogen H2+Br2=HBr+HBr, in addition to the energy expended in decomposing the hydrogen and bromine molecules, energy is also expended in converting the liquid bromine into the gaseous condition, and probably less heat is developed by the combination of bromine and hydrogen than by the combination of chlorine and hydrogen, so that the amount of heat finally developed is much less than is developed in the formation of hydrochloric acid.

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.

Thus, chlorine enters into reaction with hydrogen, and removes hydrogen from hydrogenized bodies, far more readily than bromine; and hydrochloric acid is a far more stable substance than hydrobromic acid, hydriodic acid being greatly inferior even to hydrobromic acid in stability.

Glauber showed how to prepare hydrochloric acid, spiritus salis, by heating rock-salt with sulphuric acid, the method in common use to-day; and also nitric acid from saltpetre and arsenic trioxide.

Libavius obtained sulphuric acid from many substances, e.g.

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.

A masterly device, initiated by him, was to collect gases over mercury instead of water; this enabled him to obtain gases previously only known in solution, such as ammonia, hydrochloric acid, silicon fluoride and sulphur dioxide.

Hydrochloric acid was carefully investigated at about this time by Davy, Faraday and Gay Lussac, its composition and the elementary nature of chlorine being thereby established.

In the same year Berzelius discovered selenium in a deposit from sulphuric acid chambers, his masterly investigation including a study of the hydride, oxides and other compounds.

Balard completed for many years Berzelius's group of " halogen " elements; the remaining member, fluorine, notwithstanding many attempts, remained unisolated until 1886, when Henri Moissan obtained it by the electrolysis of potassium fluoride dissolved in hydrofluoric acid.

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.

Balard discovered chlorine monoxide in 1834, investigating its properties and reactions; and his observations on hypochlorous acid and hypochlorites led him to conclude that " bleaching-powder " or " chloride of lime " was a compound or mixture in equimolecular proportions of calcium chloride and hypochlorite, with a little calcium hydrate.

Serullas and Roscoe; Davy and Stadion investigated chlorine peroxide, formed by treating potassium chlorate with sulphuric acid.

Davy also described and partially investigated the gas, named by him " euchlorine," obtained by heating potassium chlorate with hydrochloric acid; this gas has been more recently examined by Pebal.

Notwithstanding the inconsistency of his allocation of substances to the different groups (for instance, acetic acid was placed in the vegetable class, while the acetates and the products of their dry distillation, acetone, &c., were placed in the mineral class), this classification came into favour.

However, in 1833, Berzelius reverted to his earlier opinion that oxygenated radicals were incompatible with his electrochemical theory; he regarded benzoyl as an oxide of the radical C 14 H 1Q, which he named " picramyl " (from 7rucp6s, bitter, and &uvyalk, almond), the peroxide being anhydrous benzoic acid; and he dismissed the views of Gay Lussac and Dumas that ethylene was the radical of ether, alcohol and ethyl chloride, setting up in their place the idea that ether was a suboxide of ethyl, (C2H5)20, which was analogous to K 2 0, while alcohol was an oxide of a radical C 2 H 6; thus annihilating any relation between these two compounds.

Thus, he interpreted the interaction of benzene and nitric acid as C6H61-HN03 = C 6 H 5 NO 2 +H 2 0, the "residues" of benzene being C 6 H 5 and H, and of nitric acid HO and N02.

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.

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.

The same methyl iodide gave with potassium cyanide, acetonitril, which was hydrolysed to acetic acid; this must be C(Coch) a H b H c H d.

This acid with silver nitrite gave nitroacetic acid, which readily gave the second nitromethane, CH a (NO 2) b H c H d, identical with the first nitromethane.

This acid gives with silver nitrite the corresponding nitromalonic acid, which readily yielded the third nitromethane, CHaHb(N02),Hd, also identical with the first.

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.

But on the other hand, it is readily converted by hydrobromic acid into normal propyl bromide, CH 3 CH 2 CH 2 Br.

A similar behaviour has since been noticed in other trimethylene derivatives, but the fact that bromine, which usually acts so much more readily than hydrobromic acid on unsaturated compounds,, should be so inert when hydrobromic acid acts readily is one still.

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.

The introduction of hydroxyl groups into the benzene nucleus gives rise to compounds generically named phenols, which, although resembling the aliphatic alcohols in their origin, differ from these substances in their increased chemical activity and acid nature.

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.

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.

Ladenburg (Ann., 1875, 179, p. 163) to be symmetrical trimethyl benzene; terephthalic acid, the remaining isomer, must therefore be the para-compound.

Substitution of the Benzene Ring.-As a general rule, homologues and mono-derivatives of benzene react more readily with substituting agents than the parent hydrocarbon; for example, phenol is converted into tribromphenol by the action of bromine water, and into the nitrophenols by dilute nitric acid; similar activity characterizes aniline.

Of other syntheses of true benzene derivatives, mention may be made of the formation of orcinol or [3 s]-dioxytoluene from dehydracetic acid; and the formation of esters of oxytoluic acid (5-methyl3-oxy-benzoic acid), C6 H3 CH3.

Another hexa-substituted benzene compound capable of direct synthesis is mellitic acid or benzene carboxylic acid, C6(000H)6.

Strong oxidation breaks the benzene complex into such compounds, as carbon dioxide, oxalic acid, formic acid, &c.; such decompositions are of little interest.

More important are Kekule's observations that nitrous acid oxidizes pyrocatechol or [I.2]-dioxybenzene, and protocatechuic acid or [3.4]- dioxybenzoic acid to dioxytartaric acid, (C(OH) 2 COOH) 2 (Ann., 1883, 221, p. 230); and 0.

Carius showed that potassium chlorate and sulphuric acid oxidized benzene to trichlorphenomalic acid, a substance afterwards investigated by Kekule and 0.

Potassium chlorate and hydrochloric acid oxidize phenol, salicylic acid (o-oxybenzoic acid), and gallic acid ([2.3.4] trioxybenzoic acid) to tri chlorpyroracemic acid (isotrichlorglyceric acid), CC13 C(OH)2 C02H, a substance also obtained from trichloracetonitrile, CC1 3 CO CN, by hydrolysis.

We may also notice the conversion of picric acid.

This substance is transformed into hexachlor-R-pentene oxycarboxylic acid (3) when digested with water; and chromic acid oxidizes this substance to hexachlor-R-pentene (4).

These compounds are both decomposed by water, the former giving dichloraceto-trichlorcrotonic acid (4), which on boiling with water gives dichlormethylvinyl-a-diketone (5).

The heptachlor compound when treated with chlorine water gives trichloraceto-pentachlorbutyric acid (6), which is hydrolysed by alkalis to chloroform and pentachlorglutaric acid (7), and is converted by boiling water into tetrachlor-diketo-Rpentene (8).

This latter compound may be chlorinated to perchloracetoacrylic chloride (9), from which the corresponding acid (to) is obtained by treatment with water; alkalis hydrolyse the acid to chloroform and dichlormaleic acid (I I).

When thus chlorinated phenol (I) yields trichlor-o-diketo-R-hexene (2), which may be hydrolysed to an acid (3), which, in turn, suffers rearrangement to trichlor-R-pentene-oxycarboxylic acid (4).

Bromine water oxidizes this substance to oxalic acid and tetrabromdichloracetone (5).

Kekule (Ann., 1883, 221, p. 230), however, reinvestigated this acid; he showed that it was dibasic and not tribasic; that it gave tartaric acid on reduction; and, finally, that it was dioxytartaric acid, HOOC C(OH) 2 C(OH) 2 COOH.

Strecker to be trichloracetoacrylic acid, was more favourably explained by his formula than by Ladenburg's.

By reducing terephthalic acid with sodium amalgam, care being taken to neutralize the caustic soda simultaneously formed by passing in carbon dioxide, A" dihydroterephthalic acid is obtained; this results from the splitting of a Para-linkage.

By boiling with water the acid is converted into the dihydroterephthalic acid.

This acid is converted into the acid by soda, and into the Q2 tetrahydro acid by reduction.

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

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.

Experiments showed that the second acid was much more difficult to esterify than the first, pointing to the conclusion that Claus' formula for benzene was more probable than Kekule's.

This is obviously unsymmetrical, consisting of an aliphatic and an aromatic nucleus; Claus explained the formation of the same phthalic acid from the oxidation of either nucleus by supposing that if the aromatic group be oxidized, the aliphatic residue assumes the character of a benzene nucleus.

He applied himself more particularly to the oxygen compounds, and determined with a fair degree of accuracy the ratio of carbon to oxygen in carbon dioxide, but his values for the ratio of hydrogen to oxygen in water, and of phosphorus to oxygen in phosphoric acid, are only approximate; he introduced no new methods either for the estimation or separation of the metals.

If it possesses an alkaline or acid reaction, it must be tested in the first case for ammonia, and in the second case for a volatile acid, such as sulphuric, nitric, hydrochloric, &c.

Sulphur dioxide, recognized by its smell and acid reaction, results from the ignition of certain sulphites, sulphates, or a mixture of a sulphate with a sulphide.

Cyanogen and hydrocyanic acid, recognizable by their odour, indicate decomposable cyanides.

Hold a small portion of the substance moistened with hydrochloric acid on a clean platinum wire in the fusion zone' of the Bunsen burner, and note any colour imparted to the flame.

The metallic film is tested with 20% nitric acid and with bleaching-powder solution.

Arsenic is insoluble in the acid, but immediately dissolves in the bleaching-powder.

The black films of antimony and bismuth and the grey mottled film of mercury are slowly soluble in the acid, and untouched by bleaching-powder.

The black films of tin, lead and cadmium dissolve at once in the acid, the lead film being also soluble in bleaching-powder.

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.

Certain substances are insoluble in all these reagents, and other methods, such as the fusion with sodium carbonate and potassium nitrate, and subsequent treatment with an acid, must be employed.

For this purpose the cold solution is treated with hydrochloric acid, which precipitates lead, silver and mercurous salts as chlorides.