The Phosphates of America. 139 



parties, what appears upon its face to be an equitable arrangement 

 in this connection. The. market price of the phosphate rock is 

 fixed at a certain sum per unit of phosphate of lime, and it is agreed 

 that this rock may contain a certain amount of oxides of iron and 

 alumina without affecting its price. This tolerated amount, how- 

 -ever, must not exceed three per cent, by weight of the mass, and every 

 additional per cent, of oxides of iron and alumina is to be compen- 

 sated for by a proportionate deduction from the total quantity of 

 phosphate of lime. 



To justify such a deduction, it is necessary to remember that in 

 the initial stage of superphosphate manufacture, a great deal of 

 free phosphoric acid is produced, which, in the presence of oxides 

 of iron and alumina, enters into combination with them to form 

 phosphates in the following proportions : 



Oxide of iron to phosphoric anhydride 1 : 0,88 



Oxide of alumina to phosphoric anhydride 1 : 1,37 



Ratio of the equally combined oxides to the acid 1 : 1,13 



It follows from this that every per cent, of these equally 

 combined oxides causes 1.13 per cent, of phosphoric anhydride 

 (P 2 O 5 ) to become insoluble in water. Where "reverted" phos- 

 phates are valueless, therefore, the European manufacturer is jus- 

 tified in declining to pay for what will bring him no return for his 

 money . 



A working example of this arrangement may serve to make it 

 more clear, and will specially emphasize the necessity for conformity 

 of analysis between shipper and consignee. We give an instance 

 which actually turned out as follows : 



A cargo of phosphate rock was shipped from one of our ports 

 to Liverpool, in fulfilment of a contract, embodying the above 

 arrangement in regard to iron and alumina, and fixing the price 

 of the material at 25 cents per unit of phosphate of lirne. 



The analysis of the cargo (1000 tons) by the chemists at the 

 ports of shipment, and arrival, respectively, showed the following 

 variations: 



Shipment. Arrival. 



Phosphate of lime 78.30 77.10 



Oxides of iron and alumina (combined) 2.95 5.01 



These results were contested by the shippers, and the sealed 

 samples, taken and reserved at both ports, were handed to four 



