368 HH. Wurtz on the Preparation of Pure Sulphates. 
soluble impurities, may be used directly in ordinary cases, 
although a portion of the oxyd of copper also is thereby precipi- 
tated. Deutoxyd of barium is of course also applicable. 
n cases where the presence of a little dime in the product is of 
no moment, as for the use of the calico-printer and manufacturer 
of pigments, carbonate of lime may be substituted for that of 
y ta. 
In addition it may be remarked that if the blue vitriol con- 
tains traces of manganese, as is extremely liable to occur, this 
contamination, as would appear from the observations of Schén- 
bein* and Wolcott Gibbs,+ must also be entirely remove 
The same treatment is evidently applicable to some other sul- 
phates, and I therefore present it as a general method for the 
removal of iron from the sulphates of bases precipitated with 
difficulty by carbonate of baryta, namely, those of the alkalies, 
magnesia, manganese, zinc, cadmium, mercury, nickel, cobalt and pro- 
toxyd of iron. Of these the most important one practically is the 
sulphate of magnesia. The mode of proceeding with this would 
be precisely similar to that with the copper salt, as it would be 
also with the sulphates of zinc, cadmium, mercury, nickel, and 
the alkalies. With regard to the manganous sulphate, it must be 
remembered that deutoxyd of lead, as observed by Schonbem, 
wholly precipitates sulphate of manganese from its boiling solu- 
tion; so that the deutoxyd must be used only in small excess 
over the necessary quantity. The same precaution applies, 1n 4 
modified manner, to the treatment of the cobaltous sulphate, 
cause Gibbs states that the salts of this metal are also per? 
precipitated by long boiling with an excess of the deutoxy4, 
assing first to a higher state of oxydation. k 
As to the protosulphate of iron, I have already (New Yor 
Jour. Pharmacy, i, 229) recommended the use of carbonate © 
or the removal from it of sesquioxyd of iron. 
same paper (which has, I believe, entirely escaped notice : 
other Journals, owing to the irregularity with which the 6 
of 
iat reduced to protox — 
_ To return again to the sulphate of magnesia, before eel 
the subject, I must add that the treatment with carbonate © 
baryta, according to a former observation of my own,t must 7 
‘ogg. Annalen, Ixxviii, 162. 
tributions to i Am, Jour. Sci. [2], xiv. 204. 
: . Gaz, 1852, 268; Ph. J.,and gent 
rk Jour. Pharm., i, 161; also Ch. Gaz 
Ol. J, 125, 2753 also quoted in Lieb. & Kopp’s J o 
ee 
