CHROMIUM. 123 



his observations deduced the ratio between the molecular 

 weights of the two salts. 



In his earlier paper* the mode of procedure was about as 

 follows: The two salts, weighed out in quantities having 

 approximate chemical equivalency, were placed in two small 

 flasks, and to each was added 100 cc. of a ferrous chloride 

 solution and 30 cc. hydrochloric acid. The ferrous chloride 

 was added m trifling excess, and, when action ceased, the 

 amount unoxidized was determined by titration with a 

 standard solution of anhydrochromate. As in each case 

 the quantity of ferrous chloride was the same, it became 

 easy to deduce from the data thus obtained the ratio in 

 question. I have reduced all of his somewhat complicated 

 figures to a simple common standard, and give below the 

 amount of chromate equivalent to 100 of chlorate : 



I20. IlS 

 120.371 

 120. 1 38 

 120.096 

 120.241 



120. iSi 



Mean, 120.191, i .02S 



In his later paperf Kessler substituted arsenic trioxide 

 for the iron solution. In one series of experiments the 

 quantitj' of anhydrochromate needed to oxidize 100 parts 

 of the arsenic trioxide was determined, and in another the 

 latter substance was similarly compared with the chlorate. 

 The subjoined columns give the quantit}^ of each salt pro- 

 portional to 100 of AsjOg : 



K^Cr^O^. KCIO,, 



98.95 41.156 



9S.94 41. 1 16 



99.17 41.200 



98.98 41-255 



99.08 41.201 



99.15 41.086 



41-199 



Mean, 99.045, ± .02S 41.224 



* Poggend. Annal., 95, 208. 1855. 

 t Poggend. Annal., 113, 137. 1S61. 



