Superphosphate 11 



3. Again supposing equation (2) to represent what 

 happens when superphosphate is made, what is the 

 highest per cent of P2OS it is possible to have in super- 

 phosphates? 



4. What per cant of P2O5 is present in ordinary 

 superphosphata? Name the substance represented by 

 the symbol P2O5. 



5. What per cent of tricalcium phosphate is found 

 in natural phosphates? 



6. Which would use the more sulfuric acid, a raw 

 rock carrying 60 per cent tricalcium phosphate and 

 5 per cent calcium carbonate or a rock carrying 55 per 

 cent tricalcium phosphate and 10 per cent calcium 

 carbonate? 



7. What gases escape during the action of the sul- 

 furic acid on the rock phosphate? Which is poison- 

 ous? 



8. What compounds are found in the raw rock? 

 In the dissolvd rock? The student cannot give, for 

 example, calcium oxide, CaO, or phosphorus pentoxid, 

 P2O5, as compounds present in either the raw or dis- 

 solvd rock altho such compounds are well known and 

 moreover are represented in the table of analysis. In 

 the raw and dissolvd rocks the lime and the phosphoric 

 acid are in combination and the student should give, 

 as well as he can, the actual lime and phosphorus com- 

 pounds that are present. 



9. How could phosphoric acid be made by a process 

 similar to that for making superphosphate? 



10. How could the acid phosphate be made into a 

 neutral salt? How would the solubility change? 



11. Write a symbol for another acid calcium phos- 

 phate; name the compound. 



12. How is the test made for soluble phosphate? 



13. Describe the test for lime. 



