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of manures, a confusion which almost universally resulted to the 

 disadvantage of the purchaser. Consequently, leading agricultural 

 chemists in recent years have discarded the use of the term phos- 

 phate in manure analyses, and have confined themselves simply to 

 the essential plant food in the manures, namely, the phosphoric 

 acid, distinguishing between the three kinds, water soluble, citrate 

 soluble, and insoluble. The " water soluble " is that form which is 

 most readily available, and every one per cent, of it in a ton of 

 manure is worth, at average Melbourne prices, about 6s. ; S3 that 2 

 percent, would be worth 12s ; 10 per cent. 60s.; 15 per cent. gos., 

 and so on. The "citrate soluble" is not soluble in water, but is 

 soluble in weak solutions such as are contained in the soil, or are 

 exuded from the roots of plants. It is somewhat less valuable than 

 the water soluble, and every one per cent, in a ton of manure may 

 be taken as worth 4.9. 6d. That which is called insoluble " is not 

 absolutely insoluble ; it is, however, only very slowly soluble in the 

 soil. It requires strong acids to bring it quickly into solution. 

 Every 1 per cent, of this form in a ton of manure may be taken as 

 worth about $s. 



It is advisable when buying superphosphates and other manures 

 of the same class to pay attention simply to the percentage of 

 phosphoric acid, and to neglect altogether any statements as to the 

 amount of " phosphates." It is greatly to be desired that manure 

 merchants and vendors should altogether discard the use of the 

 term phosphates, a term which really misleads farmers, and tends 

 to perpetuate ignorance as to the real nature of manures. 



The confusion arising from the use of the term " phosphates" is 

 well illustrated by what has been reported to me recently in regard 

 to concentrated and ordinary superphosphate. Concentrated 

 superphosphate contains 45 or 46 per cent, of phosphoric acid 

 nearly all water soluble. It is offered now at £13 10s. per ton. 

 Last year it was offered at £12 10s. The ordinary superphos- 

 phates vary somewhat, but generally they contain about 17 to 19*9 

 per cent, total phosphoric acid, of which two-thirds is water soluble. 

 They are generally sold at £5 per ton. 



Now 17 per cent, of phosphoric acid, if combined with lime, 

 would form 37 per cent, ordinary phosphate of lime, 37 is a larger 

 and more imposing figure than 17; and it is easy to confuse far- 

 mers by talking about 37 per cent, phosphates. I am told that 

 ordinary superphosphates are being commonly advertised as con- 

 taining 36 to 48 per cent, soluble phosphate : and to farmers who 

 have intended buying concentrate 1 superphosphate it is being said 

 " Why should you pay £14 10 s. per ton. for a manure containing 

 45 per cent, phosphoric acid, when you can buy what we offer, 

 containing nearly the same amount, nearly 36 to 38 per cent, 

 soluble phosphate, for only £5 per ton?" 



To compare manures one with another, it is necessary to always 

 use the same terms ; either they must all be valued in terms of 

 phosphoric acid, or else they must all be valued in terms of phos- 

 phate of lime. It will never do to sometimes use one system and 

 sometimes the other? 



