ies, by the property, first rightly investigated by Stange, of being converted in the air, by the absorption of oxygen, into an acid, into the benzoic acid, and which appeared to lay claim to the highest interest from the manner in which it arises from bodies apparently so different. Another peculiarity, which long since drew the attention of chemists and pharmaceutists to the oil, is its containing prussic acid, whose presence seems to bear fixed relations to the nature of the oil. Among the many researches to which these properties have given rise, we mention only the latest by Robiquet and Boutron-Charlard.* As one of the facts most worthy of remark, they observe in their essay, that the fluid oil of bitter almonds, as a whole has its constituents in the almonds and appears to proceed from these constituents first by the action of water. For by the use of alcohol, it disappears altogether and can then in general be no more produced from the almonds; but in place of it they obtained a crystallizable body, formerly unknown to exist and which appeared to them to be the only cause of the peculiar bitter taste of the almonds, and one of the compound elements of the fluid bitter almond oil.†

We have been obliged to leave out of the limit of the present essay, the consideration of the question, whether this oil exists ready formed in the almond, or is generated in the course of the producing process from the fixed constituents, and a closer examination of amygdalin and its connection with the supposed generation of the oil. The clearing up of this point must be made the subject of particular experiments. To fix firmly the station from which the inquiry took its rise, we make the general remark beforehand, that in consequence of our experiments, we believe that there is a body composed of three elements, always remaining the same in its behavior towards other agents, and which can be considered not alone as the radical of benzoic acid, but at the same time as the root perhaps with slight variations of a multitude of similar combinations. But here we

* Annales de Chimie et de Physique, Vol. xliv. 352.

In the same essay, Messrs. Robiquet and Boutron-Charlard, express their conviction of the preexistence of benzoic in hippuric acid; now the chief reason on which they rely is an evident error in the Annales de Chemie, V. 43. p. 197, thus instead of saying "Si l'on cesse de chauffer au moment même qu'on sent les vapeurs sulphureuses qu'on mêle la masse noire avec de l'eau ei qu'on la fasse bouillir avec de la chaux, l'acide hydrochlorique en separe ensuite de l'acide benzoique," it should read, "n'en separe point ensuite de l'acide benzoique."

The conclusion as drawn from the unrectified phrase, is in itself contradictory; and this caused the correctness of the sentence to be questioned, which the German copy would have confirmed.

venture to assert, that it would be improper to look for this in the camphorid, whose very existence appears to us questionable, although it is placed here by Dumas without a single demonstrative experiment. A series of phenomena intimately connected with each other was the only guide which presented itself to our view. Suffer us to say that to a certainty we believe a multitude of similar radicals will readily be discovered by calculation and spontaneous changes in the analyses of organic substances, which chemists have undertaken; but here we stop, for science is but little profited by the raising of expectations, as yet unsupported by facts.

Bitter Almond Oil.-The crude oil, which served as the material for our experiments possesses a faint yellow color, the well known peculiar odor and proved itself in all its reactions, and other relations to be a decidedly pure product. We are indebted for it to the kindness of Mr. Pelouze.

Treated with alkali, acid, or a salt of iron, this oil contains a considerable quantity of prussic acid, and apart from the air, either by itself or with potassa, readily changes into benzoic acid.

We were soon convinced that the content of prussic acid bears no relation to the formation of benzoic acid, and endeavored therefore to obtain a pure oil, free from the benzoic and prussic acids and from water. This purpose was fully accomplished in the following

manner.

The crude oil was carefully mixed with hydrate of potassa and a solution of chloride of iron by strong agitation and then submitted to distillation. The whole of the oil passed over with the water, and perfectly free from prussic acid. By means of a tube, it was separated from the water, and redistilled in a dry apparatus over freshly burned, powdered chalk.

The oil obtained in this manner is pure, free from benzoic and prussic acids and water, perfectly colorless, very fluid, and has a strong refractive power; its odor is but little different from that of the crude oil; its taste is burning aromatic. It is heavier than water, its sp. gr. being 1.043. Its boiling point is so high that we could not determine it with our thermometers, which extended not above 130° centigrade.* It is easily inflammable, burning with a bright sooty flame.

* When temperature is mentioned in this essay, the degrees will be understood to refer to the centigrade thermometer.-J. B.

Urged through a red hot glass tube, it remains undecomposed. In the air, in moist or dry oxygen, it is entirely converted in crystallized benzoic acid. In the sun's ray this change is remakably hastened, beginning in the course of a few moments. The same change takes place in the air by the presence of water and potassa, with the formation of benzoate of potassa. If these experiments be made in a glass tube closed with mercury, the rise of this metal proves the absorption of oxygen.

Beside this conversion of the oil into benzoic acid, no third body is formed.

The manner of its purification shews that it is not decomposed or changed by anhydrous alkali, but to the hydrated, its behavior is different. Heated with the hydrate of potassa, apart from the air, it forms benzoate of potassa and evolves pure hydrogen gas.

If the oil be introduced into solution of hydrate of potassa in water, or into alcohol saturated with ammoniacal gas, it is immediately dissolved, and if the air be wholly excluded, a benzoate appears which when potassa is employed, is soon deposited in large shining lamellar crystals. By the addition of water which dissolves the salt, an oily body is separated, which is no longer the oil of bitter almonds.

In the concentrated nitric and sulphuric acids, the pure bitter almond oil is soluble without change. By heating the latter solution, it first becomes a purple-red, and then black with the evolution of sulphurous acid.

From the action of chlorine and bromine, new compounds arise which will be described in another part of this essay.

The composition of this pure oil was ascertained in the usual way by ignition with the oxide of copper. To expel the hygroscopic moisture from the oxide of copper, we have employed in our experiments a small air pump invented by Gay-Lussac. Since it has not been described by himself, we take the liberty of annexing a sketch of the same; for it may undoubtedly be viewed as one of the most important improvements with which organic analysis has been enriched, both as regards its convenience in use and the safety it ensures in hydrogen examinations.

Fig. 1. is the pump alone of half the actual size; it is furnished with common bladder valves, and terminates beneath in a strong screw, to fasten it firmly for use.

Fig. 2. shews the pump as connected with the ignition tube a, which is united by means of a well fitting cork with a long tube b,

filled with chloride of. calcium. c, Fig. 2. is a glass tube about thirty inches in length fastened above to the pump by a short and broad piece of a tube, and dipping below in mercury. It has no other

object than to prove by the rise of the mercury that all the connections of cork and caoutchouc are tightly closed, and it is removed as soon as the pump is put in operation. Indeed it may be dispensed

with altogether, since the tightness may be judged of after a little practice, by the force with which the air rushes in through the opened cock d, after exhaustion.

To the table is screwed a strong wooden post e, Fig. 2. on which the pump is fastened by its screw. The moisture contained in the oxide of copper mixture is expelled at the same time with the air by exhausting the ignition tube, from which by degrees the last trace is removed, since the air dried by the chloride of calcium is often admitted by repeated exhaustions and opening of the stop-cock.

It is evident that the expulsion of moisture may be hastened, from substances from which we have to fear no loss by warmth, if the ignition tube be put into a tin tube filled with hot water.*

This small air pump presents yet another advantage, of which we frequently availed ourselves in our experiments. The oil and other fluids submitted by us to analysis possess so high a boiling point, that the small bulb filled with them, was emptied of the portions of the liquid, not before this part of the tube had almost attained a red heat. It thence frequently happened, that the gas was suddenly evolved with such violence, as to throw some oxide of copper into the chloride of lime, and thereby the experiment became unavailing, at least for the determination of hydrogen. This is completely avoided by turning the open end of the small bulbs towards the closed end of the ignition tube, introducing the oxide of copper in layers and then exhausting. The small bubble of atmospheric air in the bulbs, now suffices to expel all the contained moisture, particularly if the ignition tube be brought to a more vertical position, and exhaustion be repeated. In order not to mention the accuracy of the result disadvantageously, it may be added that this manipulation with very fluid substances is throughout superflous.

We return to the pure oil of bitter almonds. Ignited with these precautionary measures, it yielded,

I. 0.386 gramme*=1.109 carbonic acid, and 0.200 water.

* This pump may be used with great convenience for drying substances which suffer drying only in a vacuum, at the common or a slightly raised temperature. In place of the ignition tube, a short tube is fastened on which is closed beneath, or a small glass globe, in which is placed the substance to be dried.

+ The gramme is always to be understood as the weight or series of weights employed.