MANGANESE. 285 



subsequent reduction of the resulting MugO^ in hydrogen. The oxide, 

 with various precautions, was then converted into sulphate. The per- 

 centage of MnO in MnSO^ is appended : 



2.6587 grrn. MnO gave 5.6530 MnSO^. 47-032 per cent. 



2.51S5 " 5.3600 " 46.9S7 



2.5992 " 5-5295 " 47.006 " 



2.8883 " 6.1450 " 47.002 " 



Mean, 47.007, =h .0025 



J. M. Weeren, in 1890 * published determinations made by two meth- 

 ods, the one Marignac's, the other von Hauer's. From manganese sul- 

 phate he threw down the hydrated peroxide electrolytically,and the latter 

 compound was then reduced in hydrogen which had been proved to be 

 free from oxygen. The resulting monoxide was cooled in a stream of 

 purified nitrogen. After the oxide had been treated with sulphuric acid, 

 converted into sulphate, and weighed, a few drops of sulphuric acid and 

 a little sulphurous acid were added to it, after which it was reheated and 

 weighed again. This process was repeated until four successive weigh- 

 ings absolutely agreed. The results of this set of experiments were as 

 follows, with vacuum standards : 



Marignac's mean, combined with this, hardly affects either the per- 

 centage itself or its probable error. Fortunately, both Marignac and 

 Weeren are completely in agreement as to the ratio, and either set of 

 measurements would be valid without the other. In order, therefore, to 

 give Marignac's work some proper recognition, we can assume a general 

 mean of 47.004, ± .0006, without danger of serious error. 



The manganese sul{)hate produced in the foregoing series of experi- 

 ments was used, with many precautions, for the next series carried out 

 by von Hauer's method. It was transferred to a porcelain boat, dried at 

 260° to avoid errors due to retention of water taken up in the process of 

 transfer, and then heated to constant weight in a stream of hydrogen 

 sulphide. Before weighing, the sulphide was heated to redness in hy- 

 drogen and cooled in the same gas. The results, with vacuum weights, 

 were as follows : 



* Atom-Gewichtsbestimmung des Mangans. Inaugural Dissertation, Halle, 1890. 



