144 



ELEMENTS OF AGRICULTURE 



stituents of a fertilizer, they enable him to tell whether 

 the manufacturer is charging to'o much for his article, 

 and what are the relative values of different brands of 

 fertilizers. x\nd, finally, they warn the farmer that 

 there is very little in a name or brand, for in not a few 

 instances manufacturers have been known to sell the 

 same article under many different names or brands. 



Questions 



1. From what two sources are the phosphates of ferti- 

 lizers derived? 2. Name the States in which the best 

 known deposits of phosphate rock are found. 3. What is 

 the difference between land rock and river rock? 4. How 

 does the land rock usually occur in the soil? 5. How does 

 the phosphate rock from different localities differ in ap- 

 pearance? 6. All phosphate rock contains compounds of 

 what element? 7. With what two elements is the phos- 

 phorus of phosphate rock usually combined and what is the 

 compound called? 8. On what does the value of phosphate 

 rock principally depend? 9. About how much calcium 

 phosphate should good rock contain? 10. With what other 

 elements is a part of the phosphorus combined? 11. How 

 are the insoluble phosphates changed into soluble com- 

 pounds in the soil? 12. Describe the process of manufac- 

 turing soluble phosphates. 13. What becomes of the sulphu- 

 ric acid used to make soluble phosphates? 14. What are the 

 soluble phosphates called? 15. What is meant by soluble 

 phosphoric acid, what by available, and what by total? 

 16. What is the difference between raw bone and steamed 

 bone? 17. About how much calcium phosphate does each 

 contain? 18. How are fertilizers valued? 



PROBLEM 



Calculate the value of a ton of fertilizer containing 3 per 

 cent nitrogen, 9 per cent available phosphoric acid, and 2 

 per cent potash; nitrogen being valued at 14 cents a pound, 

 phosphoric acid at 4 cents, and potash at 5 cents. 



