Ter.nanent Colours of Opah Bodies. '185 



'ferruginous matter diffufed through them, and 

 repeatedly wan;iing the remaining aflies in a 

 lufficient quantity of waiter. 



By mixing afhes, thus purified, with glafs, 

 together with an additional portion of borax, I 

 obtained an opake enamel remarkable for its 

 whitenefs. 



From all thefe premifes it appears, that the 

 earth, which forms the folid fubdance of plants 

 is ivhiie; that it is feparable from the colouring 

 matter by feveral means; that, whenever it is 

 cither pure and unmixed, or diffufed through 

 tranfparent colourlefs media, it exhibits its 

 ivhilenefs ; and is the only vegetable matter ivhkh is 

 endued with a refie5tive fo-joer. 



I have hitherto defcrrbed feveral cafes, in whicli 

 the ivhite matter of plants may be brought to view, 

 by the removal of the coloured particles which 

 covered it. Its expofure may alfo be effeded by 

 other means. 



It is well known that the vapour of burning 

 fulphur whitens red rofes. This effefl is gene- 

 rally attributed to the vitriolic acid arifing from 

 the fulphur. But fuch an explanation is certainly 

 erroneous, becaufe the vitriolic acid, applied to 

 the rofes thus whitened, reflores their red colour. 



As fulphur is compofed only of phlogifton and 

 vitriolic acid, and as the whitenefs is not caufed 

 •by the acid, it is evident that it is effcded by the 

 phlogifton. 



I expofed 



