Answer to Mr. Farley. ■ 291 



with water. Silk I have also coloured by the same process ; 

 but the colour was not so rich, — it was that of the hortensia 

 rose. 



I have since proved the quality of the colour thus applied to 

 flax and silk, both with soap and with slight acids, and I have 

 remarked that it does not detach itself. The only effect pro- 

 duced is, that the acids make the colour pass to a red more lively, 

 and more like scarlet, and the soap on the contrary makes it turi^ 

 to violet. 



Flax and silk coloured with this substance preserve, even after 

 being dried, the odour of amber which distinguishes the lac. 



The solution of colouring matter in the alkaline carbonates 

 is precipitated by solutions of tin or of alum into beautiful lacs, 

 which are either red or violet according as the liquor remains 

 acid or alkaline after the precipitation. These lacs appear to 

 me very substantial. 



I cannot doubt, after the experiment I have made, slight as it 

 is, that the colouring matter in question may be employed with 

 success both for dyeing and painting. It would, however, be 

 desirable to procure a quantity sufficient for making greater and 

 more varied experiments than the small quantity which I have 

 had has enabled me to make. 



As the carbonate of potash (ordinary potash) dissolves it with 

 the greatest facility, and as this alkali is every where to be pro- 

 cured at a cheap rate, I think it the best which can be employed 

 for extracting the lac from the hives in which it is contained. 



It would be necessary to dissolve the potash in three or four 

 parts of water, and to boil the hives in it : when the solution has 

 taken place, the liquid ought then to be strained through a 

 cloth. 



The solution should afterwards be desiccated by means of a 

 gentle heat, so as not to destroy the colouring matter, aiid then 

 put into vessels for transportation. 



When wished to be used, it will be sufficient to dissolve this 

 compound in water. 



LXXIV. Answer to Mr. Farley; ivith cursory Remarks on the 

 Blow-pipe and Safety-lamp. 



To Mr. Tilloch. 



Sir, — J. AM sorry that I have only this moment for the first 

 time seen the last Number of The Philosophical Magazine and 

 Journal. Mr. J. Farley, I find, has there introduced my name in 

 relation to an oil obtained from "oil of wine." I must consider 

 that hi.-) aniinadvcr^ioub arc at oncq precipitate and uncalled for. 



T 2 My 



