J. B. Mackintosh — Iron Sulphates from Chili. 245 



Ratio. 



S0 3 38-00 6-25 



Fe o 3 12-16 TOO 



FeO 22-51 4-114 



Na o 0-58 1-124 



H 2 6 (by difference) 26-75 19-55 



Formula 3FeO, Fe 2 3 , 5S0 3 , 18H 2 + FeO, S0 3 , H 2 

 or 4FeO, Fe 2 3 , 6S0 3 , 19H 2 



Water lost at 110° 0. =9 m 61 molecules. This cannot be re- 

 garded as a mixture of 4FeS0 4 , Aq. and (Fe 2 3 , 2S0 3 , Aq.) be- 

 cause it is perfectly ichite and not red or yellow- brown, which 

 would be the case if it was a mixture containing ainarantite or 

 No. 9. Another argument in favor of its individuality seems to 

 be the loss of one-half its water at 110° C. It bears a certain 

 similarity to copiapite, which suggests that it may be a product 

 of partial reduction of, or of action of ferrous sulphate on, 

 copiapite. This view does not seem to me to be far fetched, 

 since the analysis of the copiapite, quoted above, shows the 

 presence of a small quantity of ferrous sulphate, If we write 

 copiapite 2Fe 2 3 , 5S0 3 , 18H 2 it is seen that by the substitu- 

 tion of 3FeO for lFe 2 3 in the above formula, with simultane- 

 ous addition of another molecule of FeS0 4 we would arrive at 

 the formula adopted, viz : 



3FeO, Fe 2 3 , 5S0 3 , 18H 2 0-f-FeO, S0 3 , H 2 



8. Two other white powders associated with these minerals 

 have given the following figures : 



A. Ratio. B. Ratio. 



S0 3 47-90 599 45-61 570 



FeO 30-81 428 35-05 487 



Fe 2 3 5-64 35 5-14 32 



A1 2 3 0-65 6 



Na 2 4-42 71 0-33 5 



H 2 (difference) 10-58 588 13-87 770 



These both have as their chief constituent a ferrous sulphate 

 with one molecule of water, as shown below : 



A 428(FeS0 4 , H 2 O) + 7lNaJ3O 4 + 40(2Fe 2 O 3 , 5S0 3 , 4H„0) 

 B 487(FeS0 4 , H 9 0)+ 5Na 2 S0 4 +16(2Fe 2 3 , 5S0 3 , 18H 2 0) 



In the first of these this monohydrated ferrous sulphate amounts 

 to about 70 per cent of the material and in the second to about 

 78 per cent. This same compound also appears in the copia- 

 pite analysis. This form of ferrous sulphate is far more stable 

 than melanterite, which, indeed, changes into this form very 

 readily by loss of water when protected from oxidizing influ- 

 ences. 



Am. Jour. Sci.— Third Series, Vol. XXXVIII, No. 225.— Sept., 1889. 

 16 



