VOL. XC.] PHILOSOPHICAL TRANSACTIONS. 735 



6. Or, when taken out of the acid, if it was first well washed in distilled water, 

 and then boiled, it was also dissolved, and formed a pale yellowish solution: this, 

 by evaporation and cooling, became a jelly, which was again soluble in boiling 

 water; and was precipitated, like gelatin, by the tanning principle and more slowly 

 by nitro-muriate of tin. 7- If the nitric acid in which the substance was im- 

 mersed was not sufficiently diluted, or if heat was applied, the whole was rapidly 

 dissolved, with a considerable effervescence, and discharge of nitrous gas. 8. This 

 solution was yellow, like the former, the colour being intense, in proportion to 

 the quantity dissolved; and it was also changed to a deep orange or yellowish 

 brown by the addition of ammonia, without depositing any precipitate, unless a 

 large quantity had been dissolved. 9. The nitric solutions of this substance, when 

 evaporated, afforded much the same appearances as those of gelatin, but the coal 

 which remained was less spongy. 10. This substance, whether of sponge, horn, 

 quill, hair, nail, or tortoise-shell, &c. was strongly distinguished from gelatin, by 

 the effects produced when boiled with caustic fixed alkali ; for animal soaps were 

 formed, exactly similar in every property excepting colour, and the whole of the 

 original substance was completely dissolved. 11. During the process, a consider- 

 able quantity of ammonia was discharged; and, if the alkali was in excess, some 

 coal was deposited. 



12. When the animal soap was dissolved, diluted with distilled water, and filtra- 

 ted, if an acid, such as the acetous or muriatic, was added, a copious precipitate 

 was obtained, which was re-dissolved by an excess of acid. 13. This precipitate, 

 being collected on a filter, appeared at first like a yellow or brownish viscid sub- 

 stance, which, when dry, was like a thick coat of varnish, or dried white of egg, 

 and in like manner was brittle, and broke with a glossy fracture. 14. It burned 

 like quill or tortoise-shell, leaving a spongy coal; and, when distilled, afforded 

 products like those obtained from the bodies above-mentioned. 15. It was not 

 readily soluble in dilute acids; and was acted on by nitric acid and ammonia, like 

 the substances from which it had been obtained; the properties also of its solu- 

 tions in nitric acid and ammonia were similar. 16. With caustic lixivium of pot- 

 ash it readily combined, and again formed animal soap. 17- It was not quite so 

 insoluble in boiling water as quill or tortoise-shell; and the water in which it had 

 been boiled was not only made turbid by nitro-muriate of tin, but yielded a pre- 

 cipitate when infusion of oak-bark was added, after the manner of gelatin. 



These experiments proved, that this precipitate was the same as the original 

 substance from which it had been obtained; and that the only change it 

 had suffered, was that of being rendered rather more soluble in boiling 

 water. The whole series of experiments on the various bodies lately enu- 

 merated, convinced me also, by the similarity of results, that they es- 

 sentially consisted of one and the same substance, modified in texture by the 

 degrees of organic arrangement and by the occasional presence, and different pro- 



