104 METALLOSALINES. [IV. 



by the direct action of oil of vitriol and old sheet-copper, or 

 by solution of precipitated hydrate of copper in the acid, or 

 by lixiviating roasted copper-pyrites. 



Pure Sulphate of 31anganese. — Eisner thus prepares it : 

 1 pt. sulphur is vrell mixed and heated with 5| pts. binoxide 

 of manganese, so that sulphurous acid escapes, and protoxide 

 of manganese remains. When 2 equiv. of this oxide are 

 treated with less than 2 equiv. of oil of vitriol, so that a por- 

 tion of the oxide remains uncombined, this portion removes 

 all the iron from the sulphate, and gives a good vitriol by 

 solution and crystallization. White vitriol may be similarly 

 made free from iron. (Eisner, in Hoifmann's Mittheilungen, &c.) 



It would be better to use a little less sulphur, so as to leave 

 a small part of the manganese in its state of binoxide, that 

 by peroxidizing the iron the latter may be more effectually 

 removed. A good proportion for a good ore (containing but 

 little silica) is 1 pt. sulphur, 6 pts. black oxide of manganese, 

 and 5 pts. oil of vitriol. The same principle has been applied 

 to Epsom salt, by heating the solution with a portion of mag- 

 nesia itself. It is also applicable to solutions of nickel and 

 cobalt. But in all these cases it is necessary that the iron be 

 in the state of sesquioxide, or be brought into this state. 



Borate of Co])per, a green Pigment. — 16 pts. blue vitriol, 

 and 25 pts. borax are separately dissolved in water, the solu- 

 tions poured together, and the bluish-green precipitate, washed 

 wifeh cold water, is first dried at common temperature and then 

 by warmth. The dried precipitate is then heated in a hessian 

 crucible to a low red-heat, but not to fusion, and ground. 

 Bolley proposes it for oil and porcelain painting (Bolley, 

 Schweiz. Gewerbebl. 1847, 28). Dr. Eisner remarks that the 

 color varies in different experiments, and that a certain degree 

 of heat is requisite to its production. 



Blue Sulphuret of Copper. — Alexander and Walter give the 

 following method of preparing it (Buchner's Repert. d. Pharm. 

 1847). Black oxide is prepared by precipitating blue vitriol 

 solution by caustic soda or potassa (lime ?), washing it well 

 and drying it. A mixture of 2 pts. of this oxide, 2 pts. 



