VOL. LXXXIV.] PHILOSOPHICAL TRANSACTIONS. 431 



6. From purified white lac nothing could be extracted by water ; nor from 

 the lac in its impure state, except a bitterish mucilage. 7- White lac turned to 

 a black coloured substance by boiling it in concentrated sulphuric acid. The 

 mrxture was then diluted with water, and by means of the filter a carbonaceous 

 matter was separated, which on being made red-hot burnt in the air without 

 flaming. The filtered liquid, on evaporation to dryness, afforded no alkaline or 

 other residue. 8. Glass covered with a thin coat of white lac was kept im- 

 mersed in oxygenated muriatic acid gaz, and also in water saturated with this 

 gaz, for several months, without producing any apparent change on the colour 

 of the lac, or in its other properties. 



Q. On about 1 00 grs. of white lac were poured 400 grs. of concentrated nitrous 

 acid. In a few minutes time the acid became of a deep orange colour, and on 

 making it hot nitrous gaz discharged, with an ebullition of the liquid. A fresh 

 discharge of nitrous gaz took place on adding more nitrous acid. On applying 

 caloric, to make the acid boil and to melt the lac, this substance was totally dis- 

 solved ; but on standing to cool it seemed to be wholly separated from the acid, 

 and was rendered white. On diluting with water the acid from which the lac 

 had separated itself, a very slight curdy precipitation took place ; and the same 

 appearance took place on adding ley of pot-ash. On evaporating this acid to 

 dryness, a very small residue of lac was obtained. Having dissolved a little of 

 this substance by boiling it in concentrated nitrous acid, and poured the solu- 

 tion while hot into water, a very copious precipitation instantly took place, of 

 the lac rendered quite white. 



10. One hundred grs. of the substance under examination were totally dis- 

 solved, and very readily, in 500 grs. of volatile oil of turpentine. While this 

 solution was hot it was clear, but on cooling it became opaque and white. On 

 evaporation the whole of the lac was recovered. 



1 1 . Fifty grs. of white lac readily dissolved in 500 grs. measure of sulphuric 

 aether, in the temperature of 80°. This solution was not unctuous, or resinous ; 

 the lower part of it was like an emulsion, and the upper part was transparent 

 and limpid ; but both parts contained the substance dissolved. On evaporation 

 the lac was recovered in the form of a light white powder, which on melting 

 became a brittle yellow solid, as heavy as before solution. 



12. One hundred grs. of white lac being digested in 1000 grs. measure of 

 alcohol, the specific gravity of which was as 835 to 1000, about ^ of the sub- 

 stance soon dissolved ; and the solution when cold was opaque, white, and thick, 

 as saturated solution of soap in hot spirit of wine appears on cooling. By re- 

 peated affusions of alcohol on the residue of these 100 grs. all but about 15 grs. 

 was dissolved ; and this residue did not appear to be different from lac which had 

 not been digested in this menstruum. This solution afforded on evaporation a 

 light white opaque powder, which on being melted was a brittle, yellow, heavy 



