AND OBSERVATIONS ON LAC. Q"J 



Thefe properties of* the colouring fubftance of lac, efpe- 

 cially its partial folubility in water, and in alcohol, and its 

 infolubilify in ether", together with the precipitates formed 

 by alumina and muriate of tin, indicate that this fubftance 

 is vegetable extract, perhaps flighily animalized by the coc- 

 cus. 



The effects which it produced on gelatin, alio demonftrate 

 the prefence of tannin; but this very probably was afforded 

 by the fmall portions of vegetable bodies, from which the 

 flick lac can feldom be completely feparated. 



Properties of the Refin of Lac. 



This fubftance is of a brownifli-yellow colour; and, when Refin of lac. 

 put on a red-hot iron, it emits much frnoke, with a peculiar 

 fweet odour, and leaves a fpongy coal. 



It is completely foluble in alcohol, ether, acetic acid, nitric 

 acid, and the lixivia of potalh and foda. 



Water precipitates it from alcohol, ether, acetic acid, and 

 partially from nitric acid ; and it polIefTes the other general 

 characters of a true refin. 



Properties of the Gluten of Lac. 



It has been already obferved, that when fmall pieces of (hell Gluten of lac, 

 lac have been repeatedly digefted in cold alcohol, they become 

 white, bulky, and elaftic. By drying, thefe pieces become 

 brownifh and brittle ; the elaflicity is alfo defiroyed by 

 boiling water, exactly as when the gluten of wheat is thus 

 treated. 



If the pieces of fhell lac, after the digeftion in alcohol, 

 be digefted with diluted muriatic acid, or with acetic acid, 

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

 precipitated, in a white flaky ftate, by alkalis; but, if thefe 

 laft be added to excefs, and heat be applied, then the glu- 

 tinous fubftance is rediffolved, and may be precipitated by 

 acids. 



If the pieces of fhell lac, after digeftion in alcohol, be 

 treated with alkaline lixivia, then the whole is difiblved, and 

 forms a turbid folution. But, when acids are employed, 

 the chief part of the gluten is alone acted upon, and a 

 confiderable reftduum is left, confiftiug of the wax, fotne 



Vol. X.— February, 1805. H of 



