Experime?its and Olscrvat'ions on Lac. 35? 



is the active substance ; and tliis conclusion v.-ill be con- 

 firmed, by the results of subsequent expeiimeiits made 

 with the alkalis. 



In order to render lac (especially shell lac) soluble in 

 water, about j of borax is necessary; and this may be pre- 

 viously dissolved in the water, or may be mixed and added 

 together with the lac. 



The best proportion of water to that of lac is 1 8 or 20 

 to 1. So tliat 20 grs. of borax, and four ounces of water, 

 are, upon an average, requisite to dissolve 100 grains of 

 shell lac; but more water may be occasionally added, to 

 supply the loss caused by evaporation during the digestion, 

 which should be made nearly in a boiling heat. 



This solution of shell lac is turbid, and of a reddish- 

 brown colour : when considerably diluted with water and 

 agitated, a weak lather is formed ; it is decomposed by 

 acids, and the lac is precipitated in yellow flocculi, which 

 do not apparently differ from the lac originally employed. 



The general properties of the solution show, that it is a 

 saponaceous compound, which, being used as a varnish or 

 vehicle for colours, becomes (when dry) difficultly soluble 

 in water, aUhough this was the liquid employed to form the 

 solution. 



A white thick scum or cream collects on the surface of 

 this liquid, after it has been suffered to remain tranquil for 

 some time, and is found to be produced by a sort of wax, 

 which I shall more particularly notice when the analyses of 

 the varieties of lac arc described ; but, in the present case, 

 this wax appeared in some degree to be converted into an 

 almost insoluble soap by the alkali of the borax, and may 

 be regarded as the principal cause of the turbidness of the 

 .solution. 



11. The lixivia of pure soda and of carbonate of soda 

 completely dissolve the different kinds of lac ; and these 

 solutions exactly resenible those formed by means of borax, 

 excepting that they are deeper coloured. 



Rather less than -^ of carbonate of soda is required to 

 dissolve shell lac ; and this solution, when dried, is sooner 

 affected by damp or water than the solution prepared by 

 borax. 



1 2. Lixivium of pure or caustic potash speedily dissolves 

 the varieties of lac, and forms saponaceous solutions, 

 similar to tint in which borax was employed, exclusive 

 of tlie colour, which is deeper, and more approaching to 

 purpl':, 



Z 3 Lixivium 



