S4 M. Walter on the Bichromate of PercJiloride of Chrome. 



Cr3 = 1055-457 = 35-37 

 Ch6= 1327-950 = 44-51 

 O^" = 600-000 = 20-12 



The density of the vapour deduced from observation gives 

 D = 5-9 ; the value obtained by calculation by means of the 

 formula 2 Cr O^ + Cr Ch^, is equal to D = 5-48. 



3 vol. of chrome 11-6433 



6 vol. of chlorine ... J4-6760 



6 vol. of oxygen 6*6156 



32-9349 



= 5-48 



6 



The analysis and the density of the vapour of the bichro- 

 mate of the perchloride of chrome coincide therefore in re- 

 presenting this body as a combination of chromic acid and 

 perchloride of chrome ; its constitution may however be re- 

 garded in a different light, which, without being in contra- 

 diction either to the composition or to the density found, ex- 

 plains in a certain degree better its remarkable characters and 

 its little stability. Dr. Thomson having subjected this body 

 at the time to analysis, had already offered quite a peculiar 

 opinion on its constitution ; he regarded it as being formed of 

 chromic acid and of chlorine, and called it chloro-chromic acid;* 

 but this opinion could not withstand the objection of H. Rose, 

 that with this supposition the combination mustcontain 10 per 

 cent, more chlorine than obtained by analysis. But if instead 

 of representing this combination as formed of chromic acid 

 and chlorine, we look upon it as being formed of Cr O*^ 

 and chlorine, the hypothetical radical Cr O^ of chromic acid 

 (itself expressed by the formula Cr O* -\- O), acting the 

 part of a simple body similar to the oxide of carbon and to 

 benzoyl, this combination becomes analogous to the chloro- 

 oxicarbonic acid, the chlorine occupying the place of the oxy- 

 gen, which is not found in the radical of chromic acid. We 

 may therefore represent this body by the formula CrO® + Ch, 

 which agrees both with the analysis and with the density 

 found. Indeed the analysis calculated according to this for- 

 mula gives the following result : 



1 atom of chrome 351-819 = 35-37 



2 atoms of chlorine 442-650 = 44-51 



2 atoms of oxygen 200-000 = 20*12 



994-469 100-00 



* A notice of Dr. Thomson's researches will be found in Phil. Mag. and 

 Attnals, N. S. vol. i. p. 452.— Edit. 



