448 The Purchase of Artificial Manures. 



Sometimes, though not often, the figure is made to lo£>k more 

 attractive by being stated as sulphate of ammonia ; but this 

 also need cause no difficulty, if it be remembered that 

 66 lbs. of this substance are equivalent to no more than 

 14 lbs. of nitrogen or 17 lbs. of ammonia. If, therefore, 

 we take the above example, the figures mean one and 

 the same thing, whether they are stated as 37- per cent, 

 of nitrogen or 4-5 per cent, of ammonia, or 17*4 per 

 cent, of sulphate of ammonia. But a manure mer- 

 chant who failed to effect many sales for a fertiliser of ever 

 so high-sounding a name on a statement of 1 per cent, of 

 nitrogen or i'2 per cent, of ammonia might be more 

 successful with a certain class of buyer if he entered the 

 nitrogen as equal to 47 per cent, of sulphate of ammonia, and 

 yet the three figures all represent the same fact. Under the 

 Fertilisers and Feeding Stuffs Act, 1893, the invoice must 

 contain the minimum guarantee of nitrogen, stated as such. 



Phosphates or phosphate of lime may also be entered in an 

 analysis or price list in several ways, but as a rule this 

 ingredient is either stated as above or as phosphoric acid. 

 In an invoice, however, the statement must be made as 

 soluble or insoluble phosphates, as the case may be. 



The relationship between phosphates or phosphate of 

 lime, whether soluble or insoluble, and phosphoric acid is 

 quite as simple as that between nitrogen and ammonia : 

 142 lbs. of phosphoric acid always form 310 lbs. of phosphate 

 of lime, so that to convert the former into the latter one may 

 multiply by 2.2, which, though giving an answer slightly 

 above the truth, is quite accurate enough for all ordinary 

 purposes. 



If, therefore, the analysis of a manuie is returned as 12 per 

 cent, of phosphoric acid, it is equivalent to saying that it 

 contains fully 26 per cent, of phosphates. Similarly 30 per 

 cent, of phosphates is equal to nearly 14 per cent, of 

 phosphoric acid. 



Potash usually exists in manures in the two forms of 

 sulphate of potash and muriate or chloride of potash. It 

 takes 94-2 lbs. of pure potash to form 174*2 lbs. of sulphate of 

 potash, whereas the same amount of potash will form only 



