|f)2 MR » hatchett's experiments on lac. 



Refins aftcd on We find, from the experiments on lac, that this fubftance is 



kalb ldS ^ a1 ' f ° lub,e '" the alkalis ' alld '" (0me ° f the acids * But this faft 

 (confidering that refin is the principal ingredient of lac) is in 



oppofition tothegenerall} received opinion of chemifis, namely, 

 that acids and alkalis do not act upon refinous bodies. Some 

 experiments, however, which I have made on various refins, 

 gum-refins, and balfams, fully eftablifh, that thefe fubftances 

 are powerfully acled upon by the alkalis, and by fome of the 

 acids, fo as to be completely difiblved, and rendered foluble in 

 water. 

 Field of inquiry. It will be a very wide and curious field of inquiry, to 

 difcover what changes are thus produced in thefe bodies, 

 efpecially by nitric acid. Each fubftance muft form the fub- 

 ject of a feparate inveftigation ; and there cannot be a doubt 

 but that much will be learned reflecting their nature and 

 properties, which hitherto have been fo little examined by 

 chemifts. 

 Utility of refin- The alkaline folutions of refin may be found ufeful in fome 

 ous folutions. Q f t j )e arts . f or mar) y colours, efpecially thofe which are 

 metallic, when difiblved in acids, may be precipitated, com- 

 bined with refin, by adding the former to the alkaline folu- 

 tions of the latter. I have made fome experiments of this 

 kind with fuccefs ; and perhaps thefe proceffes might prove 

 ufeful to dyers and manufacturers of colours. It is probable 

 alfo, that medicine may derive advantages from fome of this 

 extenfive feries of alkaline and acid folutions of the refinous 

 fubftances. 



entire fubftance of lac is not however completely difiblved, as ap- 

 pears from the turbidnefs of the liquors. Three of the four in- 

 gredients, namely, the refin, the gluten, and the colouring extract, 

 appear to be in perfect iblutionj whilft the wax is only partially 

 combined with the alkali, and forms that imperfectly foluble fapo- 

 naceous compound which has been formerly mentioned, and which 

 remains fufpended, and difturbs the tranfparency of the folution. 



From various circumftances, it does not feem improbable, that 

 the long fought for, but hitherto undifcovered vehicle employed by 

 the celebrated painters of the Venetian School, may have been fome 

 kind of refinous folution, prepared by means of borax, or by the 

 alkalis. 



A fwipl 



