and Observations on the component Parts of Membrane. 2,79 



excepting that of being slightly tinged with yellow. In both 

 cases, therefore, the effects of boiling water and of acid were 

 similar, and were evidently most powerful on. those parts which 

 were the most gelatinous. 



As water dissolves mucilage more speedily than size, and this 

 last more readily than strong viscid glue, so are the effects of 

 very dilute nitric acid on the same substances ; and, when 

 equal quantities of dried mucilage, of eel-skin glue, and of the 

 strongest glue, were dissolved in equal quantities of the dilute 

 acid, the colour of the solutions was more intense, and the 

 change produced by ammoniac was more visible, according to 

 the order of solubility and of tenacity. 



It is well known how readily gelatin is dissolved by the 

 caustic fixed alkalies : when, therefore, the varieties of jelly or 

 glue were added to boiling lixivium of caustic potash, they were 

 soon dissolved ; and, if added to saturation, a brownish viscid 

 substance was formed. 



I did not observe that any ammoniac was produced, neither 

 was any coal deposited, after long boiling the solution in which 

 there was an excess of alkali. 



The viscid matter thus obtained, did not possess the properties 

 of animal soap ; for it neither formed a permanent lather, when 

 mixed and shaken with water ; nor, when saturated with acids, 

 did it afford any precipitate ; contrary to what happens, when 

 animal soap is thus treated. But, if the gelatinous substance was 

 not pure ; if, for example, any parts of membrane, which are not 

 soluble in water, were present, then, in proportion to the quantity 

 of this substance, the alkaline solution exhibited more or less of 

 the saponaceous characters ; but these I never observed when 

 pure gelatin was employed. 



