152 Intelligence and Miscellaneous Articles. 



of Unverdorben to a rigid examination. He obtained the gas by 

 acting on a mixture of fluoride of calcium and bichromate of pot- 

 ash by sulphuric acid ; the gas when passed into water contained in 

 a platinum vessel afforded a solution of the chromic and hydrofluoric 

 acids, from which he obtained 2-16 of fluoride of calcium = 1-031 

 of fluorine, and 0339 of chromium. A second analysis afforded 

 3-02 of fluoride of calcium, and -729 of oxide of chromium : the 

 mean of these analyses is, chromium 25'57, and fluorine 7't'4'3, in 

 100 parts. Although the mode of analysis adopted does not admit 

 of absolute certainty, yet it affords an approximation to the true 

 composition utterly at variance with the existence of a perfluoride of 

 chromium, the composition of which, to be analogous to chromic 

 acid, would be 



Chromium 33-4 



Fluorine 66'6 1000 



whilst, according to M. Rose's analysis, the constitution of this 

 substance approaches to a compound of 5, and not of 3 double eqs. 

 of fluorine to 1 eq. of chromium, in which case it would be com- 

 posed of 



Chromium 23-13 



Fluorine -87 100-0 



Tfthis gaseous body is indeed a fluoride of chromium composed of 

 5 double eqs. of fluorine to 1 eq. of chromium, the existence of an 

 analogous oxide of chromium containing 5 eqs. of oxygen and 1 eq. 

 of chromium is not improbable. 



The chlorochlomic acid of Thomson, prepared by heating a mix- 

 ture of common salt, bichromate of potash, and sulphuric acid to- 

 gether, on analysis afforded from l^^l gramme, 2-29 1 of chloride 

 of silver, and 629 of oxide of chromium, which indicate 45*6 of 

 chlorine, 35-53 of chromium, and a loss of 18-87 in 100 parts. By 

 a second analysis of this chloride prepared at another period, 3-33 

 of chloride of silver, and 0-975 of oxide of chromium were obtained 

 from 1-802 parts, which results are equal to 45-59 of chlorine, and 

 37-95 of chromium per cent. ; and considering the deficiency as oxj'- 

 gen, this chloride according to the first analysis will be a compound 

 of 2 eqs. of chromic acid and 1 eq. of chloride of chromium, which 

 by calculation is equal to 



Chromium 35-38 



Chlorine 44-51 



Oxygen 20-1 1 lOO'O 



This substance is the only known instance of a volatile combina. 

 tion containing chromic acid, and that, a volatile compound formed 

 of an oxide and a chloride. M. Rose dissents from Thomson's 

 opinion in regard to the composition of this bod)', considering it to 

 be a compound of chromic acid aod chloride of chromium, and not a 

 combination of chromic acid and chlorine ; for if we consider 

 with Thomson that all the chromium exists as chromic acid, there 

 will be, if we adopt M. Rose's analysis, an excess o 10 per cent., 

 which he attributes to impurity of the carbonate of soda employed 

 by Thomson in his analysis. 



In endeavouring to prepare a compound of selenium analogous to 



