tjG Mr. Delaval on the Caufe of the 



For the purpofe of procuring mafies made up 

 of fuch particles, I reduced feveral Tranfparent 

 Coloured Liquors to a folid confifbence, by eva- 

 poration. When a gentle heat is employed in 

 this operation, the Colouring Matter, which is 

 thus concentrated, remains unimpaired, and ca- 

 pable of again imparting its colour unaltered, 



to other liquors. 



In this ftate, the Colouring Particles reflet no 

 coIouTy and, as no light is tranfmitted through 

 them, they are Mack. 



Amongft the liquors, which I evaporated, were 

 the tinflures, and infufions, of the colouring 

 particles of red, purple, blue, and yellow flowers, 

 of logwood, brazil, fuftic, turmeric, red laun- 

 ders, alkanet, fap green, kermes, and all the 

 other Tranfparent Coloured Liquors, enumerated 

 in the preceding table, which are capable of be- 

 ino- reduced to a folid confidence, without un- 

 dergoing fuch changes, during their evaporation, 

 as render them opake. 



The opacity, which fome liquors are apt to 

 acquire from the lofs of part of their folvents, 

 arifes from various caufes, fuch as the cryftal- 

 lization of faline matters, or the coalefcence of 

 the colouring particles, into maflTes which differ 

 confiderably, in denfity, from the menftrua in 

 which they were diffolved. 



The confideration of this fubjed: is of much 

 importance to the art of dying, I have con- 



ftantly 



