29 



By the other plan : 

 IS'oo soluble phosphate. 

 ToO added. 



2005 



Difference : 'SG, or nearly four-tenths of a per cent. 



No. 3, a pure bone superphosphate and therefore containing- 

 no phosphate of iron. 



By exact method : 

 35"29 soluble phosphate. 



By the other plan : 

 36'23 soluble phosphate. 



Difference about 1 per cent. 



It will be seen from the above analysis that the method is 

 quite accurate enough to tell a farmer whether his superphos- 

 phate is good or bad without going to the expense of a professional 

 chemist's analysis every time he buys a few tons. But if he 

 finds by his own analysis that his manure is not what it should 

 be he should then have it analysed by a professional, and if he 

 has bought the manure with a guarantee that it contains a certain 

 amount of soluble phosphate, which should always be done, he 

 can recover. 



Before I conclude I will say a few words about the value of 

 the constituents of manures per unit. 



Soluble phosphates in bone manures are given 



by Sibson at 4s. 6d. per unit. 



Ditto in mineral superphosphates 4s. ,, 



Insoluble phosphates in bones or guano. ... 2s. 6d. ,, 



Ammonia 20s. ,, 



I am inclined to think the values given for soluble 

 phosphates are too high, for good mineral superphosphates 

 could be bought last spring in Canterbury market at 3s. lOd. 

 per unit, and those containing 25 per cent, of phosphates made 

 soluble came to £4 15s. lOd. per ton (that is 25 times 3s, lOd.) 

 Much more is often charged for the same quality. 



The so-called precipitated phosphates or phosphates which 

 have been made soluble, and are supposed to have gone back 

 partially into the insoluble state, I have taken no notice of, for 

 the reason that chemists are not at all agreed about them and 

 there is no reliable method of estimating them. The written 

 description of the method of analysis makes it appear rather 

 complicated, but it is very simple and easy Avhen put intO' 

 practice, and if anyone should find any difficulty on trying it, I 

 shall at all times be glad to give any assistance I can. 



