', Clarice — Note on Mineral Analysis. 



Art. XXXIIL— Note on Mineral Analysis; Notes upon some 

 Fluorides; and Note on Molecular Volumes; by F. W. CLARKE, 

 S.B., Professor of Physics and Chemistry.— Laboratory Notes 

 from the University of Cincinnati. Nos. I to III. 



I. Note on Mineral Analysis. 



In 1868,* the writer called attention to the fact that certain 

 very refractory minerals are easily rendered soluble by fusion 

 with a mixture of sodium fluoride and acid potassium sulphate. 

 He now finds that in many cases, and with but little loss of 

 power, common salt may replace the fluoride, the mode of 

 manipulation remaining the same. The finely pulverized min- 

 eral is to be mixed with three parts of the chloride in. a 

 platinum crucible, and the mixture covered with 

 fifteen parts of the acid sulphate in small fragments. 



r an ordinary Bunse 1 i'> ilame. 



aplete. The fused mass, after 

 cooling, detaches readily from the crucible, and shows upon 

 its smooth under surface no traces of un decomposed assay. 



This method is not by any means equal to the original 

 process with sodium fluoride, either in speed or in g* 

 of application ; still, in some cases, it is convenient. Sodium 

 fluoride is expensive, and not always immediately to be 

 obtained; hence the desirability of a substitute. Perhaps my 

 new observation might better be stated thus: that whenever a 

 mineral is resolvable by fusion with the acid sulphate alone, 

 the action is very much facilitated by the addition of common 

 salt. 



The new fusing mixture will probably prove to be most 

 serviceable in the analysis of refractory iron ores and of 

 chromite. The latter mineral, after fusion with chloride and 

 bisulphate, furnishes a green mass completely soluble in dilute 

 hydrochloric acid. Or this mass may be treated directly with 

 strong nitric acid and potassium chlorate, after the method of 

 Storer and Pearson, and all the chromium oxidized at once to 

 chromic acid. Precipitation of the chromium as 

 chromate is then possible, but not wholly convenient. Several 

 unsuccessful efforts were made to carry out the ox 

 the chromium in the course of the fusion itself. With the 



pari 

 fr;K-t : 



fluoride or chloride, sodium nitrate or potassium eaJ 

 ts mixed. Then upon fusing with the acid sulpha 

 oxidation ensued, but in no case did more than a sm; 

 of the chromium seem thus to be affected. 

 * This Journal, March, 1868. 



