Benzo-ether is obtained by heating benzoic alcohol with boracic anhydride in a closed vessel to about 250° for several hours. The boracic acid must then be extracted with boiling water and a weak solution of sodic carbonate, and the residue must be distilled at a temperature of about 590°; benzo-ether passes over, and a hydrocarbon (H2) remains in the retort:

Benzo-hydrochloric ether when heated in a sealed tube with ammonia furnishes the volatile base toluylia, E,H,N, which corresponds to ethylia in the ethylic series. When benzoic alcohol is mixed with oil of vitriol, it yields a compound acid (HC,H,SO), corresponding to the ethylsulphuric. It may be obtained in crystalline plates.

(1439) BENZOINE (Є14H122); Fusing pt. 248° (120° C.).—It has been already mentioned that when the vapour of benzoyl hydride is transmitted over heated caustic potash, potassic benzoate and hydrogen are produced: but if the crude essence be agitated with its own bulk of a saturated alcoholic solution of potash, the oil is slowly changed into a mass of crystals, which are isomeric with benzoyl hydride: the same change occurs if the pure hydride be digested with an alcoholic solution of potassic cyanide: to the substance thus formed the name of benzoine has been given. The presence of hydrocyanic acid is necessary to the production of this metamorphosis; but the mode in which it acts is entirely unknown, since it remains in the liquid, unaltered in amount, after the change has been effected.

Benzoine may be obtained in a state of purity by crystallizing it from boiling alcohol, in which it is readily soluble. Ether also dissolves it freely. It is nearly insoluble in cold water, but is somewhat soluble in boiling water. Benzoine is destitute of odour and of taste: at 248° it fuses, and at a higher temperature it may be distilled unaltered. If its vapour

be transmitted through red-hot tubes, it is re-converted into the essential oil of bitter almonds. Cold sulphuric acid dissolves it with the production of a violet colour. Benzoine has been regarded as (€1H1Ð1⁄2,H), or (H,H), or as the hydride of a new radicle. stilbyl* (HO), but the series to which it gives rise has been

When disulphotoluol (sulphide of benzoene) is distilled, it yields, among other products, a hydrocarbon termed by Laurent stilbene (E14H12), owing to its tendency to crystallize in silky groups resembling in appearance the mineral stilbite, and the derivatives of this body constitute the stilbylic series.

BENZILIC ACID-BENZILE.

613

hitherto but incompletely investigated. When benzoine is fused. with caustic potash, it becomes converted into potassic benzoate with evolution of hydrogen: but if it be boiled with an alcoholic solution of potash, a beautiful violet-coloured solution is formed which is gradually bleached by boiling, whilst hydrogen is disengaged, and potassic benzilate is formed:

Benzilic or Stilbylic Acid [(H,H); Fusing pt. 248° (120° C.)] is obtained by decomposing a hot solution of the potassic benzilate, by means of hydrochloric acid: it crystallizes from the solution on cooling, in brilliant needles. Benzilic acid is sparingly soluble in cold water, but is freely dissolved by alcohol and by ether; at 248° it melts to a colourless liquid, which becomes red at a higher temperature; when heated still more strongly it is decomposed, emitting fumes of benzoic acid, and violet vapours; the latter may be condensed into a reddish, acrid, oily liquid. Benzilic acid is soluble in oil of vitriol with a beautiful crimson colour, which disappears on diluting the solution. The benzilates are monobasic; those of silver and lead are white and nearly insoluble.

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(1440) Benzile (Є11H102).—When a current of chlorine is transmitted through melted benzoine so long as hydrochloric acid is evolved, hydrogen is removed and benzile is formed. It may also be obtained more readily by heating benzoine gently with twice its weight of concentrated nitric acid; benzile rises to the surface in the form of a liquid oil which solidifies on cooling; it may be purified by crystallization from ether or from alcohol, and is deposited in beautiful regular six-sided prisms, which are of a yellowish colour. Benzile is tasteless, and insoluble in water. It may be fused, and it solidifies again between 194° and 198° into a fibrous mass. At a higher temperature it may be distilled unaltered. Benzile is polymeric with benzoyl.* It contains one atom less of water than normal benzilic acid. When dissolved in a hot solution of potash it forms a violet-coloured liquid, which by boiling becomes colourless; the benzile be

*If cupric benzoate be cautiously distilled, an oily distillate passes over with the odour of geranium. It crystallizes in oblique rhomboidal prisms, which fuse at 158° (70° C.). It may be regarded as benzoyl (E,H,O), the radicle of the benzoic series. When heated with caustic potash it is readily converted into potassic benzoate while hydrogen escapes; (¤‚ο¤), + 2 KHO = 2K¤2H ̧¤ ̧ + H2.

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BENZILE-STILBYL CHLORIDE.

coming converted into potassic benzilate; €14H102 + KHO =

Benzile is soluble in about 6 parts of acetic acid, and if this solution be digested with iron it is reconverted into benzoine, the hydrogen liberated by the iron at the moment of its solution recombining with the benzile (Zinin).

Zinin states that if benzile be treated with an equivalent amount of phosphoric chloride, chlorobenzile, a white crystalline compound, is obtained, in which 2 atoms of chlorine have displaced 1 of oxygen, according to the equation :—

Benzile.

:

Chlorobenzile.

If alcoholic solutions of chlorobenzile and caustic potash be heated together, equivalent quantities of hydride of benzoyl and potassic benzoate are formed, the resulting changes being the following:

Chlorobenzile.

Potassic benz.

Benzoyl hydr.

€_HCl,O + 3 KHO = KC,H,O + C,H,O + 2 KC1 + H,O.

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5

When benzile is treated with ammonia it gives rise to a series of compounds which contain nitrogen, viz. :—

:

2.

Ꮋ Ꮎ

Benzilam.

3.

€28H22N2O2 = 2 €14H102 + 2 H ̧N - 2 H2O;

Chloride of Stilbyl, or of Benzile (,,H,CI); Boiling pt. about 518° (270° C.).—When phosphoric chloride is heated with benzilic acid, a violent reaction occurs, stilbyl chloride, phosphoryl chloride, and hydrochloric acid being formed :—

By collecting those portions which distil at a temperature above 482° (250° C.), benzile chloride is obtained in the form of a colourless oil which is denser than water. It has a powerful and peculiar odour; on exposure to air it absorbs moisture, and is converted into benzilic and hydrochloric acids; €1H1„Cl+

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(1441) Benzoine combines with ammonia, and forms two crystallizable products, which are obtained by digesting benzoine for several weeks in an aqueous solution of ammonia, viz. :

Benzoinamide.

Benzoine.

€12H36N4 = 314H122 + 4 H2N − 6 H2→;

I.

42

Benzoinam.

Benzoine.

Benzoinamide is polymeric with hydrobenzamide; when heated, it melts, and may be distilled unchanged. It is very sparingly soluble both in alcohol and in ether, even at a boiling temperature.

Besides the compounds already described, there are numerous others derived from the essence of bitter almonds, which contain sulphur; but for a description of them the reader is referred to Gerhardt's Traité de Chimie Organique, tom. iii., and to various memoirs there cited; particularly to one by Laurent (Ann. de Chimie, III. i. 291).

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(1442) HIPPURIC ACID (HЄ,H,NO, or HO,C1H ̧NO5= 179).—This acid is a constituent of the urine of the herbivora, and hence the name, from πоç, a horse, though it is most readily obtained from the urine of the cow, which, according to Boussingault, contains about 13 per cent. of it. The urine of the horse also yields hippuric acid if the animal be kept at rest, but if he be kept actively at work the greater part of the hippuric acid disappears, and benzoic acid is found in its stead. Hippuric acid, in minute quantity, is also a normal constituent of human urine, but its amount may be voluntarily increased by taking benzoic acid in any form into the system, since benzoic acid during its passage through the human body becomes converted into the hippuric, and is excreted in this form by the kidneys. If the urine be allowed to become putrid, the hippuric acid is decomposed, and benzoic acid is formed in its place. The facility with which these changes occur is explained by the fact that hippuric acid is truly a colligated benzoic compound. When hippuric acid is boiled for some hours with concentrated hydrochloric acid, it assimilates the elements of water, and is resolved into benzoic acid and glycocine, in the following manner :

Dessaignes has also shown that hippuric acid may be reproduced from benzoyl chloride and the compound of zincic oxide with glycocine:

Preparation.-Hippuric acid may be obtained by adding milk of lime to the fresh urine of cows, boiling for a few minutes, straining from the precipitated phosphates, then adding hydrochloric acid to exact neutralization, and boiling the liquid down to one-eighth of its original bulk; on adding hydrochloric acid in considerable excess to this concentrated liquid, brown crystals of hippuric acid are deposited; they may be dissolved in hot water, and decolorized by transmitting a current of chlorine: the solution on cooling deposits long, colourless, transparent needles of hippuric acid. These crystals often become milk-white when kept.

Properties.-Hippuric acid crystallizes in forms derived from the rhombic prism. It requires about 600 times its weight of cold water for solution, and is still less soluble if this liquid be strongly acidulated with hydrochloric acid; boiling water dissolves it readily, so does hot alcohol, but it is nearly insoluble in ether. Hippuric acid has a bitterish taste; its solutions redden litmus powerfully. The acid melts at a gentle heat, and appears to enter into ebullition at about 464° (240° C.), but it is in reality becoming decomposed; the distillate contains a crystalline sublimate of benzoic acid, and a reddish oil (benzonitrile) which has the agreeable odour of the Tonka bean; hydrocyanic acid is also formed at the same time, and a considerable residue of carbon is left in the retort.

Hippurates.-Hippuric acid is monobasic. Its compounds with the metals of the alkalies and with magnesium are very soluble, and are crystallized with difficulty. Acid hippurates of potassium and ammonium may be obtained. Calcic hippurate (Єa 2 €,H.NO,

3 H2O) crystallizes in beautiful rhombic prisms. The hippurate of lead is deposited from concentrated solutions in the form of a dense curdy precipitate, but it may be obtained from very dilute boiling solutions in tufts of silky needles with 2 H2O, which gradually become changed into broad brilliant quadrangular plates (Pb 2 Є,H,NO,, 3 H2O).

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Solutions of the hippurates give white insoluble precipitates with mercurous and with argentic salts: with the ferric salts they yield a characteristic brown precipitate. The hippurates when in the solid form are readily distinguished by distilling them with caustic potash, when they furnish ammonia and benzol.

Hippuric acid is soluble in concentrated nitric acid, and if this solution be mixed with an equal bulk of sulphuric acid,