178 Mr. Belaval on the Caiy'e of the 



the filter, which was afterward dried, and ap- 

 peared to be a white powder, flightly tinged 

 with yellow. This powder did not cohere to 

 the filtering paper, but was eafily feparable from 

 it. It was again foluble in water, and formed 

 with it a liquor, in all refpefls, fimilar to the 

 original infufion. 



From thefc circumftances, it appears that a 

 given proportion of water, or a fufficient degree 

 of heat, is requifite to the fokuion of the colour- 

 ing particles of fuftic. And experience evinces 

 that thofe particles, which are too grofs to pafs 

 through filtering paper, are incapable of entering 

 the pores, or firmly cohe/ing to the furface of 

 bodies. '^ 



Many dying ingredients, fuch as the colouring 

 particles of logwood, kermes, and various other 

 matters, are foluble in water, in all proportions, 

 and therefore their infufions are not fubjefb to 

 become turbid, or opake, during their evapo- 

 ration. And the folid extrafls, obtained from 

 thefe liquors, refle<5l no colour, but are black. 



I alfo formed folid maffes, by mixing with a 

 fmall quantity of drying oil, pigments, which 

 confifl: chiefly of colouring matter, unmixed with 

 opake ingredients, fuch as indigo, Prufllan blue, 

 and fap green. Thefe paints exhibit their re- 

 fpedive colours, when thin plates of them are 

 viewed by tranfmittcd light; but appear entirely 



black. 



