224-226] Analysis of Superphosphate of Lime 



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ANALYSIS OF SUPERPHOSPHATE OF LIME 



224. The general outline of the method may be seen from 

 the following table : 



Treat with water. Filter. 



Precipitate. Transfer to a plati- 

 num capsule, and burn off 

 paper and organic matter. 

 Treat with dilute HC1. Fil- 

 ter. 



Precipitate. 

 Weigh as 

 Sand. 



Filtrate. Add 



ammonia in ex- 

 cess, filter, and 

 weigh precipi- 

 tates as insolu- 

 ble phosphates. 



Filtrate. Treat with citric acid, 

 ammonia, and acetic acid. Boil. 

 Add ammonium oxalate. Filter. 



Precipitate 

 consists 

 of cal- 

 cium oxa- 

 late. Re- 

 ject. 



Filtrate. Add strong 

 ammonia and 



magnesia mixture. 

 Weigh the preci- 

 pitate as Mg 2 P 2 7 

 and calculate 



from this the 

 soluble phospho- 

 ric acid. 



225. Moisture. — Weigh out 2 grams in a porcelain 

 capsule, heat in the steam oven for about five hours, cool in 

 desiccator, and weigh ; return to oven for about half-an-hour. 

 Cool and weigh again. Repeat until weight is constant. 



226. Organic Matter. — The organic matter in a mineral 

 superphosphate is very small, but in one made from bones 

 it is considerable. Should the analyst require to know the 

 amount exactly, the following process must be carried out : 

 Two grams are weighed out into a platinum crucible, and milk 

 of lime is added until the mass is alkaline. It is then dried in 

 the air bath at 150 C. until its weight is constant. It is next 

 ignited on the Fletcher muffle furnace for twenty minutes, 

 cooled, and weighed. The difference between this weight and 

 the weight after drying at 150 C. is the weight of organic 

 matter and combined water. Should the amount only be 



