136 MANUFACTURE OF FERTILIZING MATERIALS 



dish with as little water as convenient, and let boil 

 for 30 minutes. Then render alkaline with am- 

 monia, and add ammonium oxalate in quantity 

 sufficient to precipitate all the lime, cool, and 

 make up to 500 cc. and mix well. Filter and take 

 of the filtrate lots of 25 or 50 cc. according to 

 requirements. Evaporate these down in plat- 

 inum dishes after acidifying with sulphuric acid, 

 finally igniting the residue until white. Dissolve 

 in a little water, which should give a clear solution; 

 acidify with a drop or two of hydrochloric acid; 

 add 5 cc. of platinum chloride, evaporate to a 

 pasty condition; add 30 cc. or more of strong 

 alcohol (80 per cent or over), allow to stand 

 cold for some time, and then decant on weighed 

 filter and add fresh alcohol, and repeat two 

 or three times, and then transfer to filter and 

 wash with ether; dry, cool in desiccator, and 

 weigh. From total weight deduct weight of 

 filter-paper, or a Gooch crucible with asbestos 

 filter may be used. Precipitate is K^PtCle. 

 In place of alcohol a mixture of alcohol and 

 ether is preferable in proportions of 2 to 1. 



Regarding the examination of phosphatic ma- 

 terials to be used in the manufacture of fertili- 

 zers, a few suggestions may be desirable. 



Spent bone-black and other materials con- 

 taining carbon or carbonaceous material as well 

 as phosphate rock, may be ignited to burn off 

 the organic substances, then dissolved in hydro- 

 chloric acid, and in general treated essentially 



