THE LEAD SALT is soluble.

Lactates may also be recognized by the following processes:

a. When the hydrogen compound, lactic acid, is heated to 130° C., water containing a little lactic acid distils, and the residue, on cooling, becomes a yellowish white solid, of very bitter taste, almost insoluble in water, but easily soluble in alcohol or ether. It is called "lactide," and has the formula C. H1005, and by long boiling with water is converted again into lactic acid.

B. If lactic acid be heated with concentrated sulphuric acid, almost pure carbonic oxide gas is given off, and a body resembling humin remains behind.

SALTS OF THE SUCCINIC RADICAL, OR SUCCINATES.

To the series of which succinic acid is a member, the name "oxalic acid series" has been applied. Oxalic acid, the first member, has been already described as a volatile and bibasic acid; succinic acid and the other terms of the series, or homologues of oxalic acid, present the same characteristics. Succinic acid is obtained in many ways; the most important of these are the dry distillation of amber, and the fermentation of malate of calcium.

Succinates when heated yield numerous products of decomposition, carbonic anhydride and acetic acid being among the number.

THE HYDROGEN SALT (H2 C H ̧ O ̧ or H2S), or succinic acid, crystallizes in colourless prisms belonging to the oblique prismatic or monoclinic system. It is inodorous. It melts at 180° C., and boils at 235°, forming a most pungent vapour, which, if inhaled, excites violent coughing. It dissolves in 5 parts of water at 16° C., in 2-2 parts of boiling water, and in 1·37 part of strong alcohol.

Many succinates are soluble in water; the insoluble salts dissolve readily in acetate of potassium.

THE POTASSIUM and SODIUM SALTS (K2 C, H, O and Na, CHO) are

soluble.

4

THE BARIUM and STRONTIUM SALTS are sparingly soluble in water, but dissolve in acids; in alcohol they are insoluble.

+

THE CALCIUM SALT is precipitated on boiling concentrated solutions of chloride of calcium and succinate of ammonium. Its formula is CaC, H1O̟ +aq. It is soluble in succinic, acetic, and most other acids, but insoluble, or nearly so, in alcohol.

THE MAGNESIUM SALT is soluble.

THE FERROUS SALT is a grey-green precipitate, insoluble in water, but soluble in acids,

The Ferric Salt is a reddish brown precipitate of very variable constitution. It is insoluble in water, soluble in hot solutions of succinic or acetic acid, and in most other acids.

4

THE CUPRIC SALT is green or blue. Its formula is Cu2 C1 HO1. It is soluble with difficulty in water or solution of succinic acid; it dissolves in acetic and other acids.

THE SILVER SALT is a white precipitate, produced by nitrate of silver in neutral or alkaline solutions. It is soluble in hydrate of ammonium, and dissolves slowly in water or acetic acid. It dissolves in most mineral acids.

THE MERCUROUS SALT appears to be soluble. THE MERCURIC SALT is a white precipitate.

THE LEAD SALT is a white precipitate. Its formula is Pb С HO̟. It is but sparingly soluble in water, in acetic, or boiling solution of succinic acid. In alcohol it is insoluble.

The radical of the succinates may be recognized by the following tests:a. Succinic acid, when heated in the air, evolves suffocating vapours, which burn with a pale flame. It may be sublimed in great part unchanged. B. Succinates are not blackened when heated with strong sulphuric acid.

SALTS OF THE TARTARIC RADICAL, OR TARTRATES.

The potassium salt of this radical is found in the deposit which occurs in wine casks, and which is termed "Tartar,” or “ Argol." This radical is not at present known to be a member of any homologous series; it is bibasic; none of its inorganic salts are volatile without decomposition.

Tartrates when heated evolve the peculiar odour of burnt sugar, decomposing with formation of carbonic anhydride, carburetted hydrogen gas, acetic acid, pyrotartaric acid, and other bodies.

6

THE HYDROGEN SALT (H,C, H,O, or HT), or tartaric acid, is a substance which crystallizes in fine colourless prisms belonging to the oblique prismatic system. It melts at 170° C. to a transparent colourless liquid, but does not volatilize without decomposition. When heated to a high temperature, new acids are obtained from tartaric acid. 1 part dissolves in part of cold, and in a less quantity of boiling water. This acid has the property, in common with several others, of preventing the precipitation of many oxides by hydrate of potassium or ammonium.

This radical may be recognized both by the formation of insoluble salts and by processes of decomposition.

The neutral tartrates of the first subdivision are almost the only soluble neutral salts of this radical, and their acid salts almost the only insoluble acid salts.

The Barium Salt is produced by the addition of chloride of barium to the neutral or alkaline solution of a tartrate: it is a

4

white precipitate. Its formula is Ba, C, H,O,. It is easily soluble in all ammonium salts except the hydrate; it is also soluble in hydrochloric acid.

THE STRONTIUM SALT is comparatively soluble in water, readily so in chloride of ammonium.

2

4

The Calcium Salt is produced by the addition of even the hydrate or sulphate of calcium in aqueous solution to tartrate of sodium; it is produced in larger quantity by chloride of calcium. Its formula is Ca, C, H,O,. Its precipitation is prevented, or at least retarded, by the presence of ammonium salts, in which it is easily soluble. This salt, if filtered and washed, is remarkable for its solubility in cold hydrate of potassium, its reprecipitation on boiling the alkaline solution, and its re-solution on the cooling of the liquid.

THE MAGNESIUM SALT is comparatively soluble.

THE FERROUS SALT is a green precipitate.

THE FERRIC SALT appears to be soluble.

THE ZINC SALT is soluble.

THE CUPRIC SALT is a green precipitate. Its formula is Cu, C, H,O,+3aq. It is soluble in a boiling solution of carbonate of sodium and in acids.

The Silver Salt is a white and crystalline precipitate. Its formula is Ag, C, H,O,. It is insoluble in water; in hydrate of ammonium it dissolves, forming a solution which, when boiled, deposits a great portion of the silver it contains upon the sides of the containing vessel. With proper modifications, this constitutes Petitjean's silvering process.

THE MERCUROUS and MERCURIC SALTS are white precipitates, insoluble in water, but soluble in acetic, tartaric, and mineral acids.

THE LEAD SALT is white. Its formula is Pb, C, H,O,. It is soluble in chloride of ammonium, nearly insoluble in water; it dissolves in acids.

This acid-radical may be distinguished by processes of decomposition.

a. Tartaric acid and tartrates, when heated on platinum foil,

char, and evolve inflammable gases and the peculiar odour of burnt The experiment may be performed in a test-tube open

sugar.

at both ends.

6. When a tartrate is boiled with concentrated sulphuric acid, besides the odour of burnt sugar which is evolved, and the carbon which separates rapidly, carbonic oxide gas is also formed, and may be detected by the blue flame with which it burns when a lighted taper is applied to the mouth of the test-tube employed.

The tartaric radical is usually recognized by the formation of the insoluble or sparingly soluble barium, calcium, and silver salts, and by the tests a. and ß.

SALTS OF THE CITRIC RADICAL, OR CITRATES.

The citric radical belongs to no ascertained homologous series. It is tribasic. The acid is found in many plants, especially in the fruit of the Citrus medica, or lemon, and of the Citrus aurantium, or orange.

The citrates, when heated, begin to decompose at about 230° C., evolving many volatile products, and leaving a large quantity of charcoal.

3 6

7

THE HYDROGEN SALT (H,C, H2O, or H,Ci), or citric acid, is a colourless crystalline body of the same form as the commercial acid H,Ci+aq, which occurs in prisms belonging to the right prismatic system: these hydrated crystals effloresce in the air, and form the true acid. When heated to a high temperature, citric acid yields several new acids.

The radical may be recognized both by the formation of insoluble salts and by its decomposition.

The majority of the citrates are insoluble in water. The salts of the first subdivision are, however, soluble.

THE BARIUM SALT is a white precipitate. Its formula is Ba, C, H,O,. It is soluble in ammonium salts, in a large proportion of water, and in acids.

THE STRONTIUM SALT is a white precipitate of the formula Sr, C, H,O,, soluble in many acids.

6

The Calcium Salt is a white crystalline precipitate, which

6 5

is produced in dilute solutions only on boiling; the salt partially redissolves on the cooling of the solution. Its formula is Ca, CH,O,. It is soluble in chloride of ammonium solution; it dissolves more sparingly in boiling than in cold water; it is soluble in acids and in most ammonium salts, excepting the hydrate.

THE MAGNESIUM SALT is soluble. THE ZINC SALT is but slightly soluble in water.

THE FERRIC SALT is soluble.

THE CUPRIC SALT is precipitated on boiling as a green crystalline powder. Its formula is Cu, Ci, CuHO+aq.

THE SILVER SALT is a white precipitate. Its formula is Ag, C, H,O,. It is soluble in boiling water.

6

THE MERCUROUS and MERCURIC SALTS are white precipitates. THE LEAD SALT is a white precipitate, soluble in ammonium salts.

This acid-radical may be distinguished by the following tests:a. Citric acid, when heated in a tube open at both ends, evolves irritating acid vapours; heated on platinum foil, it chars and evolves combustible gases.

B. When boiled with concentrated sulphuric acid, citric acid evolves a trace of acetic acid and a large quantity of carbonic oxide, which may be kindled. A gradual separation of carbon also takes place.

SALTS OF THE GALLIC RADICAL, OR GALLATES.

The radical of these salts is obtained by the decomposition which tannic acid undergoes when exposed in a moist condition to the action of the air or to the influence of a fermenting body. It is said to occur in the vegetable kingdom. Recent researches have shown it to be a tribasic radical.

The radical is remarkable on account of the behaviour of its hydrogen salt (gallic acid) under the influence of heat: at a temperature of from 210° to 215° C. it loses 1 eq. of carbonic anhydride, and is converted into pyrogallic acid, thus---

The latter body sublimes in flattened needles: it is remarkable for its great affinity for oxygen, which it absorbs (especially when in solution), either from