376 P. E. Browning — Analysis of Rhodoclirosite. 



acid and titrating with a standard solution of potassium per- 

 manganate. Three determinations of carbon dioxide were 

 made taking 05 gram portions, and a fourth in which 2 grains 

 were used agreed closely with the others. In these determin- 

 ations the carbon dioxide was set free in suitable apparatus 

 by the action of hydrochloric acid and heating, and weighed 

 after absorption in potassium hydrate. The analysis is as fol- 

 lows : 



Specific gravity = 3*47. 



MnO 45-02 per cent. 



CaO 11-28 



ZnO 2-32 



MgO 1-76 



FeO 0-22 



Fe,0 3 0-16 



SiO, 0-32 



CO„ 38-94 



100-02 per cent. 



The presence of silica suggested the possible presence of 

 zinc silicate (Zn. 2 Si0 4 ) as impurity ; accordingly there was 

 deducted from the ZnO found enough to balance the silica, and 

 the remaining constituents were calculated to one hundred per 

 cent. The result is given in I below. 



I. II. 



MnO 45 



CaO 11 



ZnO 1 



Mo-0 1 



FeO 



Fe,0 3 



CO„ - 39 



55 per cent. MnC0 3 73*78 per cent. 



41 CaCO s 20-37 



48 ZnCO s 2-28 



78 MgCO, 3-74 



22 FeC0 3 0-35 



16 Fe,0 3 0-16 



40 



] 00-00 



100-68 



The hypothetical composition of the mineral, calculating the 

 bases as carbonates, is given under II above. It will be seen 

 that the amount of acid (CO,) required to supply the bases 

 exceeds the amount found by 68 per cent. The ratio of 

 Mn : Ca : Mg = 64 : 2 : -44. 



In concluding this paper, the writer would express his ap- 

 preciation of the valuable advice obtained from Professor 

 Gooch during the progress of the analysis. 



Kent Laboratory, Tale University, July, 1890. 



