Fat meltssolidifies
2o58°53°
3o58°53° a 52°
4o58°53° a 52°
5o58° a 58.5°53°
6o60°55° a 54°

The examination of the liquids separated from the above crystallizations, was now taken up. Their colour was from a very deep reddish brown (No. 1o) down to light yellow, and nearly colourless (No. 6o.) In 1o, 2o, and 5o, crystals had deposited by standing, and as 2o was not corked like the rest, the deposit here was abundant; it was re-melted with addition of as much alcohol as had evaporated, and was suffered to stand for several days longer, when a drusy crystalline deposit made its appearance. The following are the melting points for these two precipitates:

Precipitate inmeltssolidifies
1o62°-63°44°5-40°
5o51°-56°44°5-43°

The fat deposited in 2o melted at 58°, and solidified at 52°, and the fat separated from the liquid of this bottle, melted at 59°5, solidified at 53°, but continued translucent down to 33°. After the above melting points, 1o and 5o were observed, the same fat was raised slowly to the melting points, and then kept for a considerable time in the thermostat, at 100°, the points were again determined, and found to be the same.

The liquids separated from the fats 1o-6o, gave the following results:

The fat from Liquidmeltssolidifies
1o36°-46°41°-?
2o ;39°-41°37°-35°5
4o[6]59°-62°40°5-35°
5o62°-66°58°-53°
6o53°-56°41°-?

The melting point of liquid 2o, does not accord with that above stated, but I note the experiments as they were observed, merely mentioning that I observed carefully, and am not conscious of having made an error. The above points seem vague, but it was impossible to fix a point definitely, as a cloudiness persisted up to the highest degree stated, so I prefer to give the limits of certainty. In 1o and 6o the solidifying points, 41°, were taken when the liquid in the capillary tubes seemed to become solid, but it remained translucent for a long time below this point, and 6o only became opaque (and that gradually) when suffered to stand in the air.

We are reminded here of Duffy’s observations upon certain isomeric transformations of the fats, (Quar. Jour. Ch. Sec. V. 197.) He noticed that stearine heated 1° above its point of solidification, became transparent, but soon after resumed its opacity; and Heintz made a similar observation. Duffy attributes this to an isomeric transformation of the fat by the heat; but it seems to me simpler until an isomerism be more distinctly proven, to assume a mixture of fats, which unite to form a definite compound under the circumstances, and which has the above mentioned property.[7] Heintz’s researches on the fats should make us look with suspicion upon fats as pure, that are only purified by crystallization.

Duffy’s remarks were made upon the glycerine compounds of the fatty acids; it appears from the above examination of the liquids 1o and 6o, as if something similar took place with the fatty acids themselves, although, with one or two exceptions, in other determinations of melting points noted in this article, I have not observed the same phenomenon of transparency.

A few experiments were now made with the alcoholic liquid 6o. A concentrated alcoholic solution of acetate of magnesia added to this liquid, produced no precipitate, but micaceous crystalline scales fell on adding acetic acid, and upon adding more acetic acid, and heating, besides these crystals, an oil floated on the surface, which solidified on cooling, and which behaved like a fat, and gave the melting point of palmitic acid, viz.: 62° (solidifies gradually from 47° to 39°.) The crystals gave a small quantity of ash when burned on platina foil, and on being decomposed by hydrochloric acid, gave a fat with the melting point of stearic acid 72°-73°, and solidifying at 60°-55°. The mother liquid contained too little fat to experiment upon. To another portion of the liquid 6o, alcoholic acetate of magnesia was added without addition of acetic acid, and the solution evaporated in a retort. The first crystals which appeared contained a fat which fused at 65°-68.5°, and solidified at 62°-58°.