Page images

as the fats; for in the case of the latter, the point of fusion being considerably below that of boiling water, the force of aggregation is in a great degree destroyed, and consequently does not oppose itself to the chemical action; whereas in the case of cholesterine, its point of fusion being much higher than that of boiling water, it remains solid, and therefore its force of aggregation opposes itself strongly to the action of potash (supposing one to exist). So then the difference of the action of a solution of potash upon these substances is not such a strong mark of distinction as it would at first sight appear to be, as it is impossible to subject them to this action under similar circumstances.

This fact is mentioned not to show that cholesterine may be a species of fat. Far from it. Far from it. It is simply to attempt to exhibit that there is no stronger reason for supposing that cholesterine is not a fat, because a boiling solution of an alkali does not act upon it, than there is for considering spermaceti a fat, because it is acted upon; as here the spermaceti is in a state of fusion, one that is favorable to this action; and the cholesterine solid, a state opposing this action.

In an article on spermaceti I stated my reasons at large for not believing this body to be a fat, properly speaking, and at the same time explained how I supposed an alkali to react upon it. It was there ranked with athal and cholesterine. I then also stated that although a boiling solution of an alkali might not react upon cholesterine, still I had no doubt that the alkali by itself, aided with a high temperature, would react upon it in a manner similar to that which it did upon spermaceti. From the kindness of M. Pelouze, who furnished me with a small quantity of cholesterine, I have been able to examine into the truth of this supposition.

The first circumstance necessary to be observed in the examination of this reaction is to have the cholesterine intimately in contact with the potash, and this is done by rubbing together equal parts of the two substances in a mortar. The mixture was placed in a watch-glass, and spread out so as to expose a large surface to the air; the watch-glass was placed on a support in a copper vessel (the air contained in this vessel could be brought to any required temperature). The experiment. being thus disposed, the vessel was heated, and by the time

that the air in the interior arrived at 248° Fah. a change began to take place in the mixture, and at 266° Fah. it was of a darkbrown color.

This was now treated with cold ether, which dissolved the unaltered cholesterine, and also a matter of a resinous character, which when dissolved in alcohol, and the alcohol allowed to evaporate spontaneously, is deposited in the form of little round concretions entirely devoid of crystalline structure. It is not soluble in any of the alkalies. What remains after the treatment by ether is of a brown color and completely soluble in water. If hydrochloric acid be added to this solution it is. decomposed, and a yellowish substance arises to the surface. This substance is soluble in ether, alcohol, potash, soda, and ammonia, as well as their carbonates. It does not crystallize. Its alcoholic solution reacts slightly acid upon litmus-paper. In fact it is an acid of a resinous character. Its combinations with alkalies have the character of soaps. Its silver-salt is of a yellow color, but soon becomes black by exposure to the light.

From the small quantity of cholesterine that was at my disposal I have not been able to obtain sufficient of the acid to examine its composition, but I have no doubt that it is a

new one.

If the mixture when heated be not well exposed to the air, very little of this acid is formed, even if we elevate the temperature as high as 300° Fah.; but, on the contrary, a considerable quantity of the resin before mentioned (soluble in ether) is formed. This though is capable of being converted into the acid by the action of potash, a high temperature, and free access of air. Thus then it will be seen that the action of potash, instead of being a means of showing that spermaceti and cholesterine are two substances of entirely different natures, affords strong evidence of their being similar bodies. Further, the action of potash upon spermaceti is to produce athalic acid and athal, the former capable of forming soaps with the alkalies, and the latter of being converted into the former by an alkali and a high temperature.

The action upon cholesterine is to form an acid (which it is impossible for me as yet to name) and a basic resin. The former forms soaps with alkalies, and the latter by the action of potash at a high temperature is converted into the former.

This article is meant as an appendix to the one on spermaceti, and as an additional proof of the analogy that exists between that body and cholesterine, they being two of a class of bodies which will no doubt be found to be tolerably numerous, and which class I propose to call pseudo-gras. Among them may be mentioned spermaceti, cholesterine, athal, ambreine, and probably stearérine and elaïérine, two fatty substances found in linseed-oil, and which M. Chevreul brought to the notice of the Academy of Sciences not long since. This class of bodies would appear to be a link between the fats and resins.



It is a fact that, notwithstanding the advanced state of the science of chemistry, we are ignorant of some of the laws that govern the relative affinities of acids for bases, and the action of neutral salts upon each other. It is true such and such acids are ranked according to what is termed their strength, and such bases are said to be more powerful than others; still from time to time facts are developing themselves that contradict these established rules. The decomposition of the sulphate of lead by certain neutral alkaline salts (Am. Jour., xlvii, 81) I thought could be explained upon a known law, that when there existed two acids and two bases in solution (the sulphate of lead being dissolved by the salts used) the stronger acid sought the stronger base, and the feebler acid had to combine with the feebler base, notwithstanding being originally in combination with an alkali. But how are we to explain the fact about to be mentioned, which, so far as my information goes, has not been previously observed? It is that the feeblest solution of the neutral phosphate of soda or potash will decompose the carbonate of lime in the cold, giving rise to carbonate of soda and phosphate of lime.

This fact was first observed while analyzing the ashes of a plant, which was fused with carbonate of soda, for the purpose of estimating the phosphoric acid. The fused mass was thrown into about four ounces of water, and digested at about 180°. Fah. for a couple of hours. The insoluble portion was separated and treated with an acid, when to my astonishment it dissolved with but a very slight effervescence; in fact, with the escape of only a bubble or two of gas, the carbonate of lime

expected not being present. It was known that this circumstance could not arise from a want of decomposition of the original matter, as it was kept fused for half an hour with four times its weight of carbonate of soda; therefore the only rational conclusion was that the phosphate of lime was in the first case decomposed by the soda, but was subsequently reformed upon treating the fused mass with water. This has been verified by direct experiment.

Twelve grains of neutral phosphate of soda and six of carbonate of lime were digested for two hours in four ounces of water at 180° Fah., when the carbonate of lime was found almost completely decomposed, and the clear solution upon evaporation furnished carbonate of soda.

Six grains of precipitated carbonate of lime added to a solution of twenty grains of phosphate of soda (equivalent · proportions of each), in one ounce of water, were kept in a vial for one month, the temperature never exceeding 65° Fah. At the expiration of this time the insoluble portion contained three and a half grains of phosphate of lime, corresponding to a decomposition of about two and a half grains of the carbonate of lime. The soluble portion indicated a corresponding portion of carbonate of soda.

Other insoluble carbonates were experimented with, as the carbonates of magnesia, strontia, baryta, and lead. The results were the same, differing only in degree. Even hydrated alumina decomposes slightly the phosphate of soda when boiled. with it for a length of time.

I tried two other neutral salts, the acids of which produce' insoluble salts with lime, to see if they would act in the same way. The chromate and the tartrate of potash were digested a length of time upon the carbonate of lime, but no decomposition ensued.

I shall not attempt to seek for an explanation of this at present, but shall go on collecting facts of a similar character, to endeavor to find out some general principle that may operate in this and in other cases. This fact itself would not be published at the present time if it were not of the greatest importance to put analytical chemists upon their guard; for but a few days ago an individual wrote to me that he was estimating the phosphate of lime in a certain class of bodies by fusing

« PreviousContinue »