On Sujjerphospkate of Lime. 



227 



the phosphate of pow-dered coprolite in the same circumstances. 

 This is true; and in speaking of the practical methods of making 

 superphosphate of lime, we shall shortly allude to the subject 

 again, but it would be useless to attempt to give to our present 

 aro^uments such a degree of refinement as this would introduce. 



In comparison with the money- value of good samples of 

 superphosphate, let us take that of one of the inferior samples. 

 No. 9, for instance, which is not by any means the worst that we 

 have met with. It v/ill be as follovrs : — 



£. s. d. 



Gypsum 50 per cent., or ^ a ton, at 20.5. . . 0 10 0 



Nitrogen at '57 per cent., equal to ammonia '69, or 



lbs. in a ton, worth • .07 



Insoluble phosphate, 18'79 per cent,, amounting in a 



ton to 420 lbs., worth 16 3 



Bi-phosphate, 2-90 per cent., amounting to 65 lbs. 



in the ton, which, at A\d.^ is worth . . . .13 0 



Giving . . . . . .£370 



as the total value of 1 ton of such a sample of superphosphate, 

 which w^ould be sold at 71-, if not more. 



But I have no hesitation in saying that such a manure is not 

 worth one-half what we have in charity given it credit for, because 

 the farmer, in buying superphosphate, does not want gypsum 

 or insoluble phosphate of lime. The manure is lought mainly 

 for its soluble phosphoric acid. And by the proportion of this and 

 the animal matter or ammonia, as indicated by the quantity of 

 nitrogen, must we be guided in fixing its relative vrorth. 



We have attempted to fix the market-price of soluble phos- 

 phate by reference to the actual cost of it in the superphosphate 

 ias supplied by intelligent miakers. It may not be amiss now to 

 inquire what may be the cost of the materials for the production 

 of a fair sample of this manure. 



By reference to page 217 the reader will find the composition 

 of a sample of superphosphate, supposed to be made by treating 

 boiled bones with l-3rd of their weight of oil of vitriol. Al- 

 though this quantity of acid is only sufficient for the decomposi- 

 tion of 2-3rds of the phosphate, the product would contain m^ore 

 soluble phosphate than any sample that has been described. 

 Boiled bones are worth from Al. IO5. to bh IO5. per ton, say 5/. 

 Oil of vitriol is worth 10/. per ton, and brown acid about 5Z. 

 The latter is a cheaper source of real acid, but it will simplify 

 matters to suppose that the oil of vitriol is employed : — 



£. s. d. 



1 ton of bones, at 5/ 5 0 0 



One-third of a ton of oil of vitriol, at 10.'. . 3 13 4 



£8 13 4 

 q2 



