and Observations on Lac. 
217 
lac may be found of much utility ; for, like mucilage, they may 
be diluted with water, and yet, when dry, are little if at all 
affected by it.* 
We find, from the experiments on lac, that this substance is 
soluble in the alkalis, and in some of the acids. But this fact 
(considering that resin is the principal ingredient of lac) is in 
opposition to the generally received opinion of chemists, namely, 
that acids and alkalis do not act upon resinous bodies. Some 
experiments, however, which I have made on various resins, 
gum-resins, and balsams, fully establish, that these substances 
are powerfully acted upon by the alkalis, and by some of the 
acids, so as to be completely dissolved, and rendered soluble in 
water. 
It will be a very wide and curious field of inquiry, to discover 
what changes, are thus produced in these bodies, especially by 
nitric acid. Each substance must form the subject of a separate 
investigation ; and there cannot be a doubt but that much will 
be learned respecting their nature and properties, which hitherto 
have been so little examined by chemists. 
The alkaline solutions of resin may be found useful in some 
of the arts; for many colours, especially those which are metallic, 
* The alkaline solutions of lac are evidently of a saponaceous nature, and, like 
other soaps, may be decomposed by acids. The entire substance of lac is not however 
completely dissolved, as appears from the turbidness of the liquors. Three of the four 
ingredients,' namely, the resin, the gluten, and the colouring extract, appear to be in 
perfect solution ; whilst the wax is only partially combined with the alkali, and 
forms that imperfectly soluble saponaceous compound which has been formerly men- 
tioned, and which remains suspended, and disturbs the transparency of the solution. 
From various , circumstances, it does not seem improbable, that the long sought- 
for, but hitherto undiscovered vehicle employed by the celebrated painters of the 
Venetian School, may have been some kind of resinous solution, prepared by means 
of borax, or by the alkalis. 
Ff 2 
