alcohol and ether. It is soluble only to a very small extent in water, though hot water dissolves more of it than cold water. This acid combines with bases, and forms a genus of salts called ambreates. With potash it combines in two proportions. The binambreate is insoluble in water, but soluble in alcohol. The neutral ambreate dissolves in water. This salt throws down yellow precipitates when dropped into solutions of chloride of calcium, chloride of barium, sulphate of copper, sulphate of iron, nitrate of silver, acetate of lead, chloride of mercury, of tin, and of gold.

No attempts have been made to determine the atomic weight of this acid, or to analyze it. But it is obvious from the phenomena of its decomposition that its only constituents are oxygen, carbon, and hydrogen.

SECTION XXXIX.- -OF CHOLESTERIC ACID.

Class I.

Div. II.

Poulletier de la Salle first examined one of the most common Cholesterine. species of biliary calculi, and by means of alcohol extracted a white substance in plates, somewhat like spermaceti. Fourcroy afterwards, considering it as analogous to the soapy matter extracted from the dead bodies which had been left in great numbers in pits in the burial ground of the Innocents in Paris, and on that account called it adipocire. Chevreul examined it in 1816, showed that it possesses peculiar properties, and on that account gave it the name of cholesterine.*

It continues solid till heated up to the temperature of 278°, Properties. when it melts. On being allowed to cool it crystallizes in plates radiating from a centre. It is tasteless and destitute of smell. It is insoluble in water, but 100 parts of boiling alcohol of the specific gravity 0.817 dissolve 18 parts of it, but on cooling, the greatest part of the cholesterine is deposited in brilliant scales. It has no acid properties, and is incapable of being converted into soap when boiled with the alkalies. It is composed, according to the analysis of Chevreul, of

Composition.

Now the smallest number of atoms that correspond with these proportions is the following:

* From xoλn (bile), and olɛgea (solid).

Sur les Corps gras, p. 153.

Cholesteric acid,

Atomic weight.

So that the atomic weight of cholesterine cannot be less than 33.5.

Pelletier and Caventou ascertained in 1817 that when cholesterine is heated with its own weight of nitric acid till no more deutoxide of azote is disengaged, there separates a yellow matter which possesses acid properties, and to which they gave the name of cholesteric acid. When the acid liquid is diluted with water, an additional quantity of cholesteric acid separates. By repeated washings in water (in which it is scarcely soluble) it may be freed from nitric acid and rendered quite pure.

Cholesteric acid has an orange colour when in mass, but if we dissolve it in alcohol and allow it to crystallize, we obtain it under the form of white needles. Its smell is somewhat analogous to that of butter. Its taste is styptic, but exceedingly slight. It is lighter than water, but heavier than alcohol. It melts when heated to 136°. At a temperature somewhat higher than that of boiling water it undergoes decomposition, being converted into an oil, water, carbonic acid, and carburetted hydrogen.

It combines readily with the bases, and forms salts called cholesterates. They have all more or less colour. Those of potash, soda, and ammonia, are very soluble in water and deliquescent. They do not crystallize, and are insoluble in alcohol and ether. All the other cholesterates examined are very little or not at all soluble. Cholesterate of barytes is red, and very little soluble. It is composed, according to Pelletier and Caventou, of

Cholesterate of strontian is insoluble in water, and has an orange colour. According to the analysis of the same chemists, it is composed of

The cholesterate of lime is very little, and that of magnesia not at all soluble in water. The cholesterate of alumina has a fine red colour while moist, but when dry it becomes darker coloured, and has lost its beauty.

Cholesterate of lead is brick red, and is composed, according to the analyses of Pelletier and Caventou, of very nearly

Now 56 represents four atoms of oxide of lead. The salt must therefore be a tetraki-cholesterate of lead.

The atomic weight of cholesteric acid, deduced from the three preceding analyses, varies too much to admit of any very accurate deductions. By cholesterate of lead it is 20, while cholesterate of barytes makes it only 16-88. The mean of the three analyses makes the atomic weight 18.15. Probably therefore it is about 18.

When cholesterate of potash is dropped into nitrate of mercury, a black precipitate falls, while with the pernitrate of mercury the precipitate is red. With copper salts an olive coloured precipitate is obtained. The cholesterate of zinc has

a fine red colour, and is little soluble in water.*

SECTION XL.
1- -OF PINIC ACID.

Class I.

Div. II.

In the year 1826 M. Baup inserted a notice in a periodical History. work, that he had discovered pinic acid in the resin called colophon, crystallized in triangular plates, soluble in 4 times its weight of alcohol, but insoluble in water, while the resin of the pinus abies yielded another acid crystallized in square plates, and soluble in 7 times its weight of alcohol, to which he gave the name of abietic acid. He states nothing farther respecting these acids in his short notice above referred to, so that it is impossible to say whether his acids be the same as those of Unverdorben.

Unverdorben had been occupied with the examination of resins for several years. He had shown, at least as early as the year 1825, that colophon possesses the characters of an acid. His account of pinic acid appeared in 1827.§ He has shown that resins are divisible into two sets, namely, those which have acid properties, and those which are indifferent. The resins from the pine tribe belong to the first set, but they are seldom pure, being generally mixed with foreign bodies and with resinous substances which are indifferent. Pinic acid may be procured from colophon or common white resin, and from common and Venetian turpentine. To obtain it pure, we may proceed as follows:

* Ann. de Chin. et de Phys. vi. 401.

+Ibid. xxxi. 108. Poggendorf's Annalen, vii. 311, and yiii. 397, 477. § Ibid. xi. 47.

Chap. I.

Properties.

Distil Venetian turpentine with water, frequently renewing that liquid, till both the more and less volatile oil of turpentine has passed over. Dissolve the residual resin in alcohol, and mix the liquid with a solution of acetate of copper in alcohol. Pinate of copper precipitates, which must be collected on a filter and washed with absolute alcohol. Then dissolve it in alcohol containing muriatic acid, and mix the solution with its own weight of water. Pinic acid falls down, and is to be freed from alcohol by boiling it in water. Pinic acid thus obtained still contains mixed with it a small quantity of resin not soluble in alcohol.

Pinic acid is hard and brittle, and becomes electric when rubbed. When procured from turpentine it is transparent and colourless. It has no smell, but is distinguished by a bitterish taste. When fused, it assumes a brown colour in consequence of the formation of colophonic acid. By an increase of the heat it flows thin, and when made to boil, at least one-fourth of it is converted into colophonic acid. When distilled in a small glass retort it gives out a little carbonic oxide mixed with carburetted hydrogen gas, with a yellowish tar, owing to the mixture of resic acid and a little water. This water contains acetic acid and a little resin, with volatile oil and odorin. The tar contains acetic acid and some colophonic acid, mixed with much pinic acid. When the distillation takes place in a large retort, almost all the pinic acid is decomposed.

It is insoluble in water, but soluble in alcohol and ether. It dissolves also in bisulphuret of carbon. It dissolves also in concentrated sulphuric acid, and is again precipitated by water. It dissolves also in oil of turpentine. When fused with the alkaline carbonates, it drives off the carbonic acid very rapidly.

Pinic acid acts pretty powerfully as an acid, but in order to judge of its activity it must be dissolved in ether. If to an etherial solution of pinie acid we add carbonate of copper, the carbonic acid is gradually driven off with an effervescence, and the oxide of copper dissolves in the solution. When acetate of copper in fine powder is added to such an etherial solution at the temperature of 60°, the salt is gradually decomposed, and the oxide of copper combining with the pinic acid colours the liquid green. Pinate of copper is decomposed by muriatic acid, sulphuric acid, nitric acid, and phosphoric acid. The carbonate, acetate, and most of the volatile vegetable acid compounds of oxide of copper, are decomposed by pinic acid: but the sulphate, nitrate, and phosphate of copper, are not altered

by it. It is curious that the etherial solution of pinic acid does not act upon black oxide of copper; at least it scarcely acquires a green colour after some weeks' digestion: neither does it decompose or dissolve carbonate of lime. But acetate of lime is readily decomposed by the alcoholic solution of pinic acid. Muriate of lime is imperfectly decomposed when fused with pinic acid. And the same remark applies to muriate of magnesia. The carbonates of potash and soda are very readily decomposed when boiled in a solution of pinic acid in oil of turpentine.

Acetic acid partially decomposes pinate of copper. There remains a mixture of pinic acid and pinate of copper. But on the other hand pinic acid, in the state of a fine powder, decomposes acetate of copper: acetic acid is disengaged and pinate of copper formed.

Pinic acid combines with the different bases and destroys their alkaline qualities. The pinates formed are usually neutral. They resemble resin in their appearance, and none of them are capable of crystallizing. They are soluble in alcohol and ether, and the alkaline pinates also in water. The alkaline pinates may be formed by digesting the solution of pinic acid in ether over an alkaline carbonate. The earthy and metalline pinates by double decomposition by adding a solution of salt containing the base to a solution of pinate of potash or soda.

Unverdorben analyzed several of the pinates in order to determine the atomic weight of pinic acid. The results were as follows:

Class I.

Div. II.

Atomic

weight.

These analyses are derived from the statements of Leopold Gmelin in his Handbuch der Theoretischen Chemie, vol. ii. p. 523, &c. They are given by Unverdorben while giving an account of the combination of colophon with bases, Poggendorf's Annalen, vii. 312. Gmelin says that Unverdorben himself rates the atomic weight of pinic acid at 55'2, but I do not know from what data he has drawn his conclusions.