Experiments and Olservations on Lac. 355 



Quantity of resin, in the shell lac which I employed, may 

 be estimated at 91 per cerit. 



When the shell lac was only reduced into small frag-^ 

 ments, these (after the separation of the first portion of 

 r«'sin) retained their figure, but were become more bulky, 

 verv elastic, and nearly white. I at first therefore suspected, 

 that some caoutchouc w^as present in lac ; but finding that 

 boiling water destroyed this elasticity, I was induced to 

 make subsequent experiments, by which I discovered, that 

 the elasticity of this residuum was principally owing to a 

 substance which appeared to possess the properties of vege- 

 table gluten. This, however, I shall more fully notice in 

 another part of the paper. 



The resin obtained from the varieties of lac is brownish 

 yellow, and is not so brittle as the generality of other 

 resinous substances. 



3. Sulphuric ether does not seem to act so powerfully 

 upon the varieties of lac as alcohol ; for, as a great part of 

 the resin is protected by the colouring matter, and by the 

 other ingredients which are insoluble in ether, it naturally 

 follows, that less of it can be separated by this liquid ihan 

 by alcohol. 



The different kinds of lac which have been digested in 

 ether are considerably softened, although in other respects 

 very little alteration is produced. Ether, therefore, is not 

 the best menstruum for lac ; but, under certain circum- 

 stances, it may be occasionally employed with advantage, 

 for the purpose of analysis. 



4. Concentrated sulphuric acid acts in the first instance 

 Gn the colouring matter of lac ; but, after a short digestion 

 in a sand-bath, the whole is converted into a reddish-brown 

 thick liquor, which soon becomes black ; and the chief 

 part of the lac is separated, in an insoluble state, re- 

 sembling coal. 



During the solution of lac in sulphuric acid, a conside- 

 rable quantity of sulphureous acid gas is evolved. 



5. When lac is digested with nitric acid, nitrous gas is 

 at first produced; the lac swells much, and is converted in- 

 to a deep yellow- opaque brittle substance, which, by a suf- 

 ficiency of nitric acid, and continuation of the digestion 

 during about 48 hours, is dissolved. 



The solution however is turbid, and, when poured into 

 a large quantity of distilled water, deposits some yel- 

 lowish flocculi, which being collected, are found to be a 

 bort of uax. 



Z 2 The 



