The Phosphates of America. 15& 



that they will remain precipitated in the acetic-acid solution as 

 phosphates, especially in the presence of sodic acetate. When 

 the liquid has become quite cold, therefore, they can be filtered 

 off, washed, redissolved in hydrochloric acid, treated again with 

 ammonia and acetic acid, made cold, filtered, washed, dried, cal- 

 cined and weighed as iron and alumina phosphates. 



If the filtrates from these operations be mixed together and 

 heated to 70 C., they may be titrated with uranic solution as usual, 

 and the quantity of P 2 O 5 found by titration, added to half the 

 weight of the phosphates of iron and alumina, will give, very 

 approximately, the total amount of phosphoric anhydride in the 

 original substance. 



ANALYSIS OF PYRITES FOR SULPHURIC -ACID' 

 MANUFACTURE. 



The sample is drawn from bulk in much the same manner as 

 that described for the sampling of phosphates, and is ground ta 

 the fineness of 100 mesh, care being taken that every particle 

 passes through the screen. The requisite quantity, say eight 

 ounces, is now put into a wide-mouthed bottle provided with a 

 tight-fitting rubber stopper, and the analysis is proceeded with. 



The necessary determinations in the pyrites most ordinarily 

 used in this country for acid manufacture are : 



Moisture. 



Siliceous matters. 



Sulphur. 



Iron. 



Copper. 



Moisture. 



One gramme of the sample is weighed between two tightly- 

 ground watch-glasses of which the tare, including the clip, i& 

 accurately known. The necessary space to allow for evaporation 

 having been adjusted, the glasses containing the powder are placed 

 in the gas-oven and kept at 110 C. until no further loss of weight 

 is observed. Three weighings should be made at intervals of 

 about one hour. The difference between the original, and the final 



