Experiments and Observations on Lac. 21 



But in addilion to all the above uses to which it is ap- 

 plied in India, as well as to those which cause it to be in 

 request in Europe, Mr. Wilkins's Hindu ink occupies a 

 conspicuous place, not merely on account of its use as an 

 ink, but because it teaches us to prepare an aqueous solu- 

 tion of lac, which probably will be found of very extensive 

 utility. 



This solution of lac in water may be advantageously em- 

 ployed as a sort of varnish, which is equal in durability 

 and other qualities to those prepared with alcohol; whilst, 

 by the saving of this liquid, u is intinilelv cheaper. 



I do not mean, however, to ass 'it that it will answer 

 equally well in all cases, but only that it may be employed 

 in many. It will be found likewise of great use as a vehicle 

 for colours ; for, when dry, it is not easily affected by 

 damp, or even by water. 



With a solution of this kind I have mixed various co- 

 lours, such as vermilion, fine lake, indigo, Prussian blue, 

 sap green, and gamboge ; and it is remarkable, that al- 

 though the t\\ o last are of a gummy nature, and the others 

 had been previously nnxed with gum (being cakes of the 

 patent water-colours), yet, when dried upon paper, they 

 could not be removed with a moistened sponge, until the 

 surface of the paper itself was rubbed off. 



In many arts and manufactures, therefore, the solutions 

 of lac may be found of much utility ; for, like nuicilage, 

 they may be diluted with water, and yet, when dry, are 

 little if at all affected by it*. 



Wc 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 



• The alkaline solutions of he are evidently of a saponaceous nature, 

 and, like other soaps, may be decomposed by acids. The entire sub- 

 stance of lac is not however completelv dissolved, as appears from the 

 t'jrbidness of the liquois. Three .if the four inj^redients; namely, the 

 resin, the gluten, and ihc colouring extract, appe.ir to be in perfect so- 

 luiion ; whilst the wax is only partially combined with the alkali, and 

 forms that imperfectly soluble saponaceous compound which has been 

 fornuriy menti>)i)cd, and wliich remains suspended, and disturbs ilic 

 transpaaucy of the solution. 



From xariuus ciicunistanccs, it docs not seem impiobabic th.at the 

 long souijht for, hut hitherto undiscovered vehicle employed by the cele- 

 br.iied p.iinters of the Venetian School, may hare been some kind of 

 rtkinoub solution, prepared by means of borax, or by the ulkalis. 



B ;; liave 



