736 PHILOSOPHICAL TRANSACTIONS. [ANNO 1800. 



portion and quality, of gelatin. But the difference in chemical properties showed 

 that this last mentioned substance, gelatin, was quite distinct from that which is 

 now under examination; and, from the resemblance of certain effects observed 

 when quill and tortoise-shell were compared with inspissated albumen, by being 

 long digested in boiling water, I was induced to make a series of comparative ex- 

 periments on albumen, similar in every respect to those which have been so lately 

 described, of which the following are the results. ] . By distillation, the coagulated 

 dry semi-transparent albumen, afforded products exactly similar to those obtained 

 from tortoise-shell, and the other substances which have just been examined. 1. A 

 spongy coal remained, of very difficult incineration; as towards the end of the 

 process it appeared vitrified, and glazed with a melted saline coat, which was how- 

 ever easily dissolved by water. The residuum was again exposed to a long con- 

 tinued red heat, and again treated with water, till at length a few scarcely visible 

 particles remained; which, as far as such a small quantity would permit to be as- 

 certained, proved to be phosphate of lime. The portion dissolved by water, which 

 was by much the most considerable, consisted principally of carbonate, mixed with 

 a small quantity of phosphate of soda. 3. When steeped in dilute nitric acid, it 

 was not soon affected ; but, after about 4 weeks, the acid began to be tinged with 

 yellow, which gradually became deeper in the course of 3 months; the albumen 

 however, though less transparent, was but little diminished. The yellow acid so- 

 lution, when saturated with ammonia, changed to a deep orange colour, and re- 

 mained transparent. 



4. The albumen which had been thus steeped in the dilute nitric acid, was im- 

 mediately immersed in ammonia ; which changed it to a deep olive colour, inclin- 

 ing to a blood red, and gradually dissolved it, without any apparent residuum. 

 This solution is of a deep yellowish brown. 



5. If the albumen, instead of being immersed in ammonia, was washed, and 

 then boiled with distilled water, it was dissolved, and formed a pale yellow liquor, 

 which, by evaporation, formed a gelatinous mass ; this, being dissolved again in 

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

 slowly by nitro-muriate of tin. 6. By concentrated nitric acid, or by the dilute 

 acid when heated, albumen was speedily dissolved, with much effervescence, and 

 a copious discharge of nitrous gas. 7. This solution was like that of tortoise- 

 shell, and the other substances mentioned in the former experiments. 8. When 

 evaporated, it afforded similar results. 9. Albumen, like tortoise-shell, quill, and 

 nail, was dissolved by boiling lixivium of caustic potash, and formed animal soap. 

 10. In like manner also, a considerable portion of ammonia was discharged ; and, 

 if the alkali was in excess, some coal was deposited. 1 1 . The animal soap ob- 

 tained from albumen, when dissolved in water, yielded a precipitate, by the addition 

 of acetous or muriatic acid ; and the precipitate was re-dissolved when the acid 

 was added to excess. 



