162 



The Phosphates of America. 



ANALYSIS OF BRIMSTONE. 



Moisture. 



In order to prevent the evaporation of moisture during grinding, 

 an average sample of the unground or only roughly-crushed ma- 

 terial weighing 100 grammes is dried at 100 C. for some hours in 

 an oven or water-bath. 



Ashes. 



Ten grammes are burnt in a tared porcelain dish and the res- 

 idue is weighed. 



Direct Estimation of Sulphur. 



Fifty grammes of the finely-ground brimstone are dissolved in 

 200 c.c. carbon bisulphide, by digesting it in a stoppered bottle at 

 the ordinary temperature, and the specific gravity of the liquid = s 

 is estimated. This must be reduced to the specific gravity at 15 C. 

 = S by means of the formula (valid up to 25 C.) S = s -f 0.0014 

 (t 15). The following table gives for each value of S the percent- 

 age in this solution, which number must be multiplied by 4 to in- 

 dicate the percentage of sulphur in the sample of brimstone : 



ESTIMATION OF SULPHURIC ACID. 



According to our experience, the amount of actual H 2 SO 4 con- 

 tained in a given bulk of chamber acid is best determined in the 

 volumetric way as described by Lunge i.e., by titrating a meas- 

 ured volume of the acid with standard soda solution, using me- 

 thyl orange as the indicator (31 grammes pure sodium oxide in 

 1 litre distilled water, standardi/ed with very accurate normal HC1.) 



