and Observations on the component Parts of Membrane. 385 



steeped in pure ammoniac, it changed to a deep orange colour, 

 inclining to blood red ; it was gradually and silently dissolved, 

 without any residuum, and a deep orange or yellowish brown 

 coloured liquor was formed. 



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 prin- 

 ciple, and, more slowly, by nitro-muriate of tin. 



7. If the nitric acid in which the substance was immersed 

 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 ammoniac, without depositing any precipitate, un- 

 less a large quantity had been dissolved. 



g. 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 considerable quantity of ammoniac 



3 D 2 



