G. S. Robertson 



23 



The results obtained with calcined Gafsa phosphate are as follows. 



Passes "100" sieve 



1st sugar extract 



2nd „ 



1st citric extract 



2nd „ 



3rd „ 



4th „ 



5th „ 



Extract totals 

 Actual totals 



The ratios in the 1st citric acid extract correspond to those in the 

 phosphate (Ca3P20g)2 6CaO . SSiOa ; those in the 2nd and 3rd citric 

 extracts to the phosphate 4Ca3P208 . 3CaO (see Florida pebble phos- 

 phate), and those in the 4th and 5th extracts to the phosphate 



ov^aolr 2'-'s 



2CaO (see calcined Belgian phosphate) 



Tunisian Phosphate. 



The ratio P2O5 : CaO in the extractions secured from Tunisian 

 phosphate are approximately 1 : 1-49. They therefore agree with the 

 ratios in Florida pebble phosphate and are in accordance with the 

 3CaO. 



formula 4Ca3P208 



Calcined Tunisian Phosphate. 



Passes "100" sieve 



The ratios P2O5 



CaO and Si02 : CaO in the 1st citric extract 



closely resemble those in the 1st citric extract of calcined Algerian 

 phosphate, and it would thus appear that the phosphate 



(2Ca3Po08 . CaO) . 6CaO . SSiOg 



