378 Mr. Hatchett's Experiments on Zoophytes , 



pale yellow liquor, which by evaporation became of a deeper 

 colour, and, when nearly dry, was suddenly reduced to a spongy 

 coal. This change was rapid ; and was attended with a consi- 

 derable effervescence, and a copious discharge of nitrous gas,, 

 not unfrequently accompanied by sparks, and sometimes flame; 

 arising undoubtedly from nitrate of ammoniac, which was formed 

 towards the end of the evaporation. 



The acid solutions of mucilage, isinglass, and pure glue, were 

 changed to a deeper yellow, when saturated by the absorbent 

 earths, by the alkalies, and especially by pure ammoniac. In 

 such cases, little or no precipitate was obtained from pure gela- 

 tinous substances ; but some faint traces of phosphoric acid were 

 discovered in these solutions. 



The effects of the dilute nitric acid on the other various 

 substances which have been mentioned, resembled those now 

 described, and kept pace exactly with those of boiling water ; 

 for, when they were immersed in equal quantities of the dilute 

 acid during a given time, the solution of the gelatin took place 

 according to the order observed in those substances, when water 

 was employed. 



As an instance of this, two pieces of skin, recently taken from 

 an ox, were subjected to experiment, as follows : 



One of the pieces was boiled in water, till the whole of the 

 cutis was dissolved; after which, the cuticle remained, although 

 very feeble in texture, while the hair did not seem to have suf- 

 fered any material alteration. 



The other piece was steeped in nitric acid diluted with about 

 four measures of distilled water. At the end of five days the cutis 

 was dissolved, and the cuticle was become of a loose and feeble 

 texture ; but the hair had not suffered any apparent change, 



