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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 6x ; so that 2 
percent, would he worth r zs. ; 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 4s. 6 d. 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 35. 
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 “ phospha'es.” 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 £13 105. per ton. 
Last year it was offered at £12 ioj. 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 concentrated superphosphate it is being said 
"Why should you pay £14 iOj. per ton. fora 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 prr 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 Hme. It will never do to sometimes use one system and 
sometimes the other? 
