2<?0 On the new Metal called Chroma 



well defined, and fome properties which may render it sp-^ 

 plicable to the arts^ 



Exp. I. A hundred parts of this mineral reduced to a fine 

 powder, were mixed with 300 parts of the faturated carbo- 

 nate of potafh, and about 4000 parts of water; and this 

 mixture was expofed for an hour to a boiling heat. I ob~ 

 ferved, id, that when thefe matters began to act upon each 

 other there was produced a ftrong effervefcencc which con- 

 tinued a long time ; 2d, that the orange colour of the lead: 

 became a brick red ; 3d, that at a certain period the whole 

 matter feemed to diffolve ; 4th, that in proportion as the cf~ 

 fervefce ice advanced the matter re-appeared under the form 

 of a grar.u'.rued powder, of a dirty yellow colour ; 5th, that 

 the liquor aflumed a beautiful golden yellpw colour. When 

 the effervefcence had entirely fubfided, and appeared to 

 have *no longer any r.&ion on the fubftances, the liquor 

 was filtered, and the metallic duft collected on the paper. 

 After being waihed and dried, it weighed no more than 

 78 parts : the potafh therefore had taken from it 22 parts. 



Exp. IT. i poured upon- the /3 parts jutt mentioned, fome 

 of the nitric acid, diluted in twelve parts cf water, which 

 produced a briik effervefcence. The greater part of the 

 matter was duTotved : the liquor aiTumed no colour, and 

 there remains \ only a fmall quantity cf powder of an orange- 

 yellow coiour. I feparated the liquor of the refiduum by 

 the help of a fyphon, wafhed the matter feveral times, and 

 united the warnings with the firft liquor. This refiduum, 

 dried, weighed 110 more than 14 parts: from which it fol- 

 lows, r at the nitric acid had diflblved 64. 



Exp. Hi. I agair. mixed thefe 14 parts with 42 parts of 

 the carbonate of potafh and the nccei'n-y quantity of water. 

 I then treated tueni as in Experiment i. and the pheno- 

 mena were the fame. The liquor, after being filtered, was 

 United to the forme.' ; and the refiduum, wafhed and dried, 

 Weighed 110 more than 2 parts, which were full red lead, 

 snd therefore thrown away. 



Exp. IV. 



