Experiments and Observations on Lac. 353 



gum or resin, which has exuded from vegetables simply 

 punctured by insects*. 



Geoffrov and Lemery obtained from lac, by distillation, 

 some acid liquor, and a butyraceous substance. Moreover, 

 GeoftVoy observes, that when stick lac was thus treated, 

 some ammonia was also obtained, but not when seed lac 

 was employed. 



He also mentions another sort of lac, brought from 

 Madagascar, and called by the natives Lit-iii-hltsic. This 

 substance, he savs, is scarcely to be distinguished from 

 bees-wax, which it much resembles in colour and odour; 

 and that it is produced by a grayish insect, much larger 

 than the chermes lacca. It is evident however, from 

 Geoftroy's description, that this substance is very different 

 from the common lac; and there can be little doubt, but 

 that it is the same as that which was a few years ago exa- 

 mined by Dr. Pearson under the name of white lac, a 

 substance resembling the Pc-la of the Chinesef. 



Geolfroy (as 1 have stated) considered lac as a sort of 

 wax; and since his time it has scarcely, if at all, been 

 subjected to chemical examination; it is not therefore 

 surprising, that the opinions of chemists concerning it 

 have been various. Chaptal adopts the opinion of Geoffroy, 

 and calls it a kind of waxij:; but Gren§ and Fourcroy || 

 regard it as a true resin. 



§ r. 



Effects of different mcnsirita on the varieties of lac. 



1. When water is poured on stick lac, which has been 

 separated from the vegetable branches, and reduced to a 

 coarse powder, it immediately begins to be tinged with 

 red ; and, with the assistance of heat, a deep coloured 

 crimson solution is formed. 



Repeated operations of this kind reduce stick lac to a 

 yellov.'ish-brown substance ; and the water no longer re- 

 ceives any colour. 



The portion thus separated from stick lac has, upon an 

 average, amounted in my experiments to about 10 per cent. 



• Mr. Kerr observes, that ss a red substance is obtnined by incision 

 fjom the plaso ticc, very analogous to lac, ir is probable, that the insects 

 have littl'- trou'ole in animalizinjj the sap of these trees, in the foimation 

 of tlieircelli. Phil. I'rans. iviii, p. 377. 



t Phil. Ttans. 1794, p. 3S3. 



J Ch^ptal's Eiciron's; Engli'h edition, vol. iii. p. 387. 



f Principle* of modern Chemistry, vol. i. p. 3bfe. 



II S.sienii Jes C tnnoi!wn>rs chimiques, tome v. p. 624. 



Vol. 20. No, 80. Jan, 1805. Z but 



