OF ARTS AND SCIENCES. 21 T 



mate of iron is precipitated, is the same as those already given for chro- 

 mate of chromic oxide and chromate of alumina, viz. : — 



Fe^Cls + 5 (KO CrOs) = 3 (KCl) + 2 (KO 2 CrOg) + FeA CrOs. 



Until the requisite amount of chromate of potash had been added to the 

 perchloride of iron, the precipitate re-dissolved ; when it became per- 

 manent, it was drained, pressed, and air-di'ied for analysis. 



Analysis 1. 



Weight of the precipitate analyzed, 0.6626 gram. 



" " water found, 0.0966 " 



" " oxygen " . 0.0395 " 



" " soluble salts found, 0.2288 « 



" " mixed precipitate of FeaOa-f- CrjOs, 0.2977 " 



From these data may be obtained by the necessary proportions, — 



Oxygen in the chromic acid of precipitate, 0.0790 



Chromic acid corresponding to this oxygen, 0.1654 



Chromate of iron corresponding to this chromic acid, 0.4287 



Chromate of iron found =z Ye^O^ -f Cr.Oa + weighed = 0.3943 

 Excess of the calculated chromate of iron over the found = 0.0344 



This error would be perfectly corrected by a loss of three milli- 

 grammes in the water determination, or as the figures stand without 

 any correction they would lead to the conclusion that the precipitate 

 was a chromate of iron of the formula Fc^Oa CrOs, but containing a 

 very small excess of chromic acid. 



Analysis 2. 



"Weight of the precipitate analyzed, 0.6590 



" " water found, 0.0990 



" " oxygen " 0.0360 



" « soluble salts found, 0.2254 



" " mixed precipitate of Fe-A + CrA, 0.2986 



From these data may be obtained by the necessary proportions, — 



Oxygen in the chromic acid of precipitate, 0.0720 



Chromic acid corresponding to this oxygen, 0.1197 



Chromate of iron corresponding to this chromic acid, 0.3597 

 VOL. V. 28 



