BONE-DUST AND SUPERPHOSPHATE OF LIME. 319 



furnish the two atoms of water for the phosphate, and the two 

 atoms for the sulphate of lime." 



" Such is undoubtedly the case," said I, " and when large quan- 

 tities of superphosphate are made, and the mixing is done by ma- 

 chinery, it is not necessary to use water. The advantage of using 

 water is in the greater ease of mixing." 



" Bone-dust," said the Doctor, " contains about 6 per cent of 

 water, and the sulphuric acid (sp. g. 1.7) contains about one-third 

 its weight of water. So that, if you take 620 Ibs. of bone-dust, 

 and mix with it 240 Ibs. of common sulphuric acid, you have in 

 the mixture 117 Ibs. of water, which is 45 Ibs. more than is needed 

 to furnish the water of combination." 



" The superphosphate produced from C20 Ibs. of bones, there- 

 fore," continued the Doctor, " would contain : 



Phosphoric acid ) (142 Ibs. 



Lime > acid phosphate < 56 



Water j ( 36 



Sulphuric acid ) (160 Ibs. 



Lime >-sulphate of lime -< 113 



Water.. ( ( 36 



Organic matter, ash, etc., of the bones* 335 



Total dry superphosphate 877 



Moisture, or loss 45 



Total mixture 9;^ Ibs. 



* Containing nitrogen, 233, B>s. 



" There is a small quantity of carbonate of lime in the bones," 

 said I, " which would take up a little of the acid, and you will 

 have a remarkably good article if you calculate that ,the 620 Ibs. of 

 bone-dust furnish you half a ton (1,000 Ibs.) of superphosphate. It 

 will be a better article than it is practically possible to make." 



" Assuming that it made half a ton," said the Doctor, " it would 

 contain 14J per cent of soluble phosphoric acid, and 2J- per cent 

 of nitrogen." 



"With nitrogen at 20 cents per lb., and soluble phosphoric 

 acid at 12c. per lb., this half ton of superphosphate, made from 

 G20 Ibs. of good bone-dust, would be worth $22.50, or $45 per ton." 



" Or, to look at it in another light," continued the Doctor, " a 

 ton of bone-dust, made into such a superphosphate as we are talk- 

 ing about, would be worth $72.58." 



" How much," asked the Deacon, " would a ton of the bone-dust 

 be considered worth before it was converted into superphosphate ? " 



" A ton of bone-dust," replied the Doctor, " contains 76 Ibs. of 

 nitrogen, worth, at 18 cents per lb., $13.68, and 464 Ibs. phosphoric 

 acid, worth 7 cents per lb., $32.48. In other words, a ton of bone- 

 dust, at the usual estimate, is worth $46.16." 



