Experiments and Olservations on Lac. 1 J 



when saturated with alkalis^ are changed to a deep reddish- 

 purple. 



11. The hxivia of potash, soda^ and ammonia, act powei:- 

 fully on this substance, and ahnost immediately form per- 

 fect solutions, of a beautiful deep purple colour. 



12. Pure alumina, put into the aqueous solution, does 

 not immediately produce any effect ; but, upon the addition 

 of a few drops of muriatic acid, the colouring matter 

 speedily combines with the alumina, and a beautiful lake 

 is formed. 



13. Muriate of tin produces a fine crimson precipitate 

 when added to the aqueous solution. 



14. A similar coloured precipitate is also formed by the 

 addition of solution of isinglass. 



These properties of the colouring substance of lac, espe- 

 cially its partial solubility m water and in alcohol, and its 

 insolubility in ether, together with the precipitates formed 

 by alumina and muriate of tin^ indicate that this substance is 

 vegetable extract, perhaps slightly anlmalized by the coccus. 



The effects which it produced on gelatin, also demon- 

 strate the presence of tannin; but this very probably was 

 afforded by the small portions of vegetable bodies, from 

 which the stick lac can seldom be completely separated. 



Properties of the Resin of Lac. 



This substance is of a brownish-yellow colour ; and, 

 when put on a red-hot iron, it emits much smoke, with a 

 peculiar sweet odour, and leaves a spongy coal. 



It is completely soluble in alcohol, ether^ acetic acid, 

 nitric acid, and the lixivia of potash and soda. 



Water precipitates it from alcohol, ether, acetic acid, 

 and partially from nitric acid ; and it possesses the other 

 general characters of a true resin. 



Properties of the Gluten of Lac. 



It has been already observed, that when small pieces of 

 shell lac have been repeatedly digested in cold alcohol, they 

 become white, bulky, and elastic. By drving, these pieces 

 bccnnie brownish and brittle; the elasticity is also destroyed 

 bv iMiiliiig water, exactly as when the gluten of wheat is 

 thus treated. 



If the pieces of shell lac, after the digestion in alcohol, 

 be digtsited with diluted niuriatic acid, or with acetic acid, 

 the greater part of the gluten is dissolved, and may be 



grecipitated in a while flaky state, by alkalis; but, if these last 

 e added to excess, and heat be applied, then the glutinous 

 substance is rcdiss(;lved, and may be precipitated by acids. 

 Vol. 21. No. 81. I'tb. \mb. ii li 



