2a5 Anahjis of the- A^rfeniates 



■\vhite bxide of arfenic, determines a new order of dlvelliug 

 affinities. 



JBut moft of the mineral aeids that have been tried have 

 been found capable of uniting with iron in two Hates ; in 

 the liate of areen oxide, and in that of red oxide, the rcli- 

 duary powder above mentioned. I was defirous to know 

 whether I could, in any. manner, imitate, by art, the lad 

 natural prockKft* I have examined, as I iiad ahvady imitated, 

 in fonie degree, an arfcuiate of copper. For this purpofe, I 

 decompoftd green fuiphate and red i'uiphato of iron, by arle- 

 niate of ammonia; and, having well wafhed and dried the 

 precipitates, proceeded to examine them. 



The green arleniate was acted upon bv beat, in the fame 

 manner as the natural one, and exhibitrd the fame appear- 

 ances. l>y the ufual methods, I found its proportions to be. 

 Oxide of iron - 43 

 Arfenic acid - 38 



Water - - 79 



100 

 This is not the fanie proportion of acid that is contained 

 in the natural arfeniate; however, I ftate them both as I 

 found them. The other artificial arfeniate, which is of a^ 

 pale greenjfh red, afl()rded, 



Red oxide of iron 

 Arfenic acid 

 Water - - 



Thele falts agree with the generality of the known falts 

 of iron; all of which contain a greater quantity of oxide, as 

 the oxide itfelf contains lefs oxvsien. 



Bv boiling with nitric acid, it was eafv to convert the green 

 arfeniate of iron into the red ; and inch is the cafe with all 

 the ialts of green oxide of iron. As, during the courfe of 

 thefe experiments, I had occafion to make fome remarks 

 upon the divers habitudes of this metal, which, as far as I 

 know, have not all been obferved, I fhall terminate the whole 

 of thele analyles (as I have already done that part of them 

 which treats of arfeniate of copper in all its known varieties) 

 by fimply Uating what has occurred to me. 



I happened to boil fome muriatic acid upon a greater 

 cfuantity of iron than the acid could dilTolve. I found a per- 

 fectly limpid and colourlefs liquor remain, which, neverlhe- 

 lefs, was a folution of muriate of iron. This colourlefs liquor 

 being decompofed by arfeniate of ammonia, the precipitate 



was 



