On Superpliosphate of Lime. 



225 



mainly for the special influence that the soluble phosphate has in 

 forcing the plant rapidly into rough leaf. If superphosphate is 

 used for a special purpose and in conjunction with other ordinary 

 manure, there would appear to be no good reason why it should 

 not be perfectly efficacious, although it contain no particle of animal 

 or vegetable matter whatever. 



Of the loss sustained by the farmer in purchasing an inferior 

 sample of phosphate of lime it would seem hardly necessary to 

 speak, did we not Is now how little care or attention is bestowed 

 on these matters. If there be any object in adding sulphuric 

 acid to bones or other phosphoric substances, and if that object 

 is the production of a soluble phosphate, it seems pretty clear 

 that some of the samples mentioned are by many times more 

 valuable than others. Not to take an extreme case, let us com- 

 pare the sample No. 7 with an average sample, such as No. 12. 

 Here we find that the soluble phosphate is double in the latter 

 what it is in the former, whilst the quantity of nitrogen is as 10 

 to 1. If the former is worth 11. per ton, which in all probability 

 would be the price paid for it, the latter must be cheap at 10/. 

 But I know that superphosphate, having the composition given 

 for sample No. 10, can be prepared, and is prepared, and sold 

 in large quantities, at 11. per ton ; and as it is reasonable to sup- 

 pose that it remunerates the dealer at this price^, it is not too 

 much to expect that there should be a corresponding value in 

 other samples sold at that price. In a former paper I attempted 

 to fix the value of the ingredients of guano, and a similar attempt 

 will now be made in reference to superphosphate, taking the 

 sample No. 10 as a standard. It will be of some importance 

 for our future guidance that we should gain an approximative 

 notion of the money value of soluble phosphate of lime. To 

 do so it will be only necessary to deduct the manurial value of 

 the nitrogen (ammonia) of the insoluble phosphate and of the 

 gypsum from that of the mixed manure, and we gain at once 

 an approach to that of the bi-phosphate. The price of ammonia 

 has been fixed at between bd. and Gf?. per lb. according as it is 

 bought in one or other of the commercial articles which furnish 

 it. Phosphate of lime, in the insoluble state, is worth about 

 Jflf. per lb. 



Gypsum in the precipitated form, as a refuse from the manu- 

 facture of stearine candles, tartaric acid, &c., can be bought in 

 almost unlimited quantity at from 155. to 205. per ton; at the 

 latter price it will be worth something more than l-4th of a 

 farthing per lb. 



The value of these three substances in a ton of sample No. 10 

 will be as follows : — 



VOL. xn. Q 



