which may he oltalned from ChrcrM, t^7 



the knowledge of chrome was a present of great value made 

 to the sciences and to society. 



Being employed at present in examining the chemical 

 properties of this metaJ, I directed my observatijns in par- 

 ticular to its oxide, or tlie combinations it may present with 

 earths, in the hope of finding the elementary green -colour 

 so loner wished for by painters. A series of experiments 

 enabled me to pubU-rh results so vciy satisfactory, that I 

 hope soon to see the green colour of chrome make a figure 

 on the pallette of the painter along with those beautiful co- 

 lours for which the art has long been indebted to those oc- 

 cupied with the natural science:;. 



Having prepaied, by the common processes, an alkaline 

 ehromate, I jioured into it a solution of mercury (id 7?ihn- 

 mum. There was formed a precipitate of a very beautiful 

 red colour, which experienced no sensible change in the 

 air. As this chromate exhibited a combination very proper-. 

 for furnishing oxide of chrome by an easy decomposition, 

 I thought that this salt mixed with an earth would give, by 

 the aid of heat, the colour I required. 



Three parts of the ciu-omate of mercury and one of aln- 

 .mine were strongly heated in a crucible. The result was a^ 

 yellow substance, slightly greenish at the parts in contact 

 "with the air. and \\ hich I fou.-d to be chromate of alumine. 



I repeated the same experiment with the same propor- 

 tions, but in a stronoer heat, and obtained a beautiful grcea 

 colour having a great deal of body, which experienced no 

 alteration either Trom the' air or from light. The scries of 

 my experiments naturally induced me to analyse the chro- 

 mate of mercury, the result of which I shall here lay before 

 the reader, as it may serve to guide thc)se who may be de- 

 sirous of procuring oxide of ciiromc, or the green colour 

 proper for painting. 



u^rialyiis of the Chromate rf Merairij, 

 Fifty crammes of the chromate of mercury were intro- 

 duced into a retort, to the neck of which was adajHed a 

 glass tube immersed in a tui), a Ik-nk being properly placed 

 to collect the sias which mit^h-t be disenirao-cd durins: the 

 operation. 



After hemg exposed for fifty mimitcs to a heat which, 

 during the last moments, was exec cdingly strong, I thoiight 

 that the whole of the mercurv must have passed over. I 

 took the apparatus from the fire. The whole of the mercur)' 

 comlenKcd \n the tub was found to amount to 40 grammes. 

 I found ihechroiufc oxidated under the form of a light re- 



gulus 



