228 



On Superphosphate of Lime, 



These quantities of acid and bones will make more than l^- ton of 

 superphosphate, because the oil of vitriol does not contain suffi- 

 cient water to furnish the gypsum with its quantity for combina- 

 tion and 10 per cent, of moisture to the product. The acid 

 will be diluted of course in the process, and the amount of 

 product will be as nearly as possible 28j cwts., at a cost for 

 materials alone of 8/. 135. 4c?., which is at the rate of about 

 Q)S. 2(1. per cwt., or 6Z. 3^. Ad. per ton. A saving of rather more 

 than 1/. on every ton of superphosphate would be effected by 

 using the brown acid instead of the oil of vitriol : but even at 

 this rate, and supposing the manure of composition, such as we 

 have described it at page 226, to be sold at 71. per ton, a margin 

 of less than 2Z. per ton would be left to the manufacturer for 

 superintendence, profit, interest of capital, labour, bags, wear 

 and tear of machinery and utensils, and delivery to his customers. 

 Whether this is sufficient to meet the exigencies of the case it is 

 not for me to say ; but without offence to the class of manure- 

 dealers, who have as fair right as any other traders to get an 

 adequate return for their capital and energies, I may perhaps be 

 allowed to say that the better the article they can produce for a 

 given price, the more widely extended will the use of this 

 valuable manure become, and the greater will be the advantage 

 derived, not only by themselves, bat also by the agricultural 

 interest to which they minister. I believe that the average 

 value and efficiency of the manure as supplied throughout the 

 country is far below what it should be and might readily become 

 with the application of sufficient intelligence and information on 

 the part of those who manufacture it. The truth is, that the 

 production of superphosphate of lime is not so easy a matter as 

 it would seem at first sight; there are many circumstances which 

 tend more or less to modify the result, and the neglect of any one 

 of the necessary precautions will lead to failure. 



With the conviction that there are many makers on the small 

 scale who would gladly receive such hints as a knowledge of the 

 chemistry of the subject will place at their disposal, I shall pro- 

 ceed shortly to recapitulate the circumstances which should be 

 taken into account in undertaking the manufacture of the 

 manure. 



Practical suggestions for the maliing of Superphosphate of 

 Lime. — The first point to be considered is the material or 

 materials to be employed. Bones form at present the great 

 staple of this manufacture ; but if the consumption should largely 

 increase, recourse must be had, to a very great extent, to the 

 mineral phosphates. Bones may be used without previous pre- 

 paration ; but it is far more economical on the whole that they 

 should have been previously boiled to remove the grease, which 



