272 M. Chevreul on Fatty Bodies, and [Oct; 



boiling, and much diluted ; as the solution cooled, it deposited 

 the pearly matter very copiously. By analyzing it in the same 

 way with the other kinds of soaps, the same results were obtained; 

 it was reduced into pearly matter and into a soap which was 

 very soluble in cold water ; these were found to be the super- 

 margarate of potash and a soap composed of the oleic acid. 

 When a portion of the oleate of potash was decomposed by tar- 

 taric acid, an oleic acid was obtained, fusible at 64*5°, of a yellow 

 colour, soluble in all proportions in alcohol of the specific gravity 

 of '821, at the temperature of 77°. The following is the compo- 

 sition of the oleates of barytes, strontian, and lead respectively. 



Oleic acid 100-00 



Barytes 31-24 



Strontian 23-18 



Oxide of lead 100-00 



The fat which was not acid, after being kept for some days in 

 a closed vessel, impregnated the confined air with an aromatic 

 odour. It was colourless, and semi-transparent like wax ; when 

 it was suddenly cooled on water, the upper surface was flat, and 

 did not present any appearance of crystallization ; while the 

 lower surface, which lay upon the water, was deeply furrowed. 

 When it was broken, it appeared to be composed of brilliant 

 plates. A quantity that had been melted in a porcelain capsule 

 was slowly cooled, and the upper surface was then crystallized in 

 small needles which were united into stars. This substance 

 melted at 176°, began to be opaque at 134-5°, and was com- 

 pletely solid at 123-8° ; it was perfectly transparent as long as it 

 remained fluid. It appeared to be soluble in alcohol in all pro- 

 portions ; the solution did not affect the colour of litmus. It 

 contained a small quantity of barytes in the proportion of -066 

 to 100. By digesting the fatty matter in successive portions of 

 alcohol, and examining the substance that was dissolved, it 

 appeared that this re-agent does not possess the power of decom- 

 posing the fatty matter. 



This fatty matter was then added to an equal weight of potash, 

 dissolved in a large quantity of water, and subjected in the 

 digester to eight successive operations, when a flexible. sapona- 

 ceous substance was procured, of a light yellow colour, fusible at 

 about 144°, and an alkaline liquor which did not contain any of 

 the sweet principle. This flexible saponaceous substance was 

 decomposed, and was found to consist of the peculiar fatty 

 matter, which was not acid, described above, and potash, in the 

 proportion of 100 of the former to seven of the potash. When 

 one part of the substance had 40 parts of water added, it lost its 

 semi-transparency and its lemon colour by absorbing the water, 

 and the mixture became milky. After being macerated for thiee 

 hours, it was boiled, and a perfect emulsion was produced, 



