220 



On Superphosphate of Lime. 



into this country to any considerable extent, in consequence of 

 the great expense of getting it on board ship ; at present, there- 

 fore, it is not likely to be of practical importance in the manufac- 

 ture of superphosphate of lime. 



Dr. Daubeny's analysis of this substance* is as follows; — 



Silica 1-70 



Peroxide of iron , . . .3*15 

 Fluoride of calcium . . . .14*00 

 Phosphate of lime . . . .81*15 



100*00 



In a small sample of this same deposit, presented to the Royal 

 Agricultural Society by Mr. Kimberley, I found 41^ per cent, of 

 phosphoric acid, equal to 85J per cent, of bone-earth phosphate ; 

 so that this phosphorite is very rich in phosphoric acid. The 

 Spanish mineral contains no carbonate ; but Dr. Daubeny found 

 in it 14 per cent, of fluoride of calcium, which, as we before 

 mentioned^ reduces the effective strength of the acid mixed with 

 it. Every 100 parts of fluoride of calcium will saturate 103 

 parts of rmZ sulphuric acid, or 120 of oil of vitriol; and allow- 

 ance must be made for this circumstance in apportioning the acid 

 to be employed. The American phosphorite has only been lately 

 introduced to our notice. It is described as occurring in beds of 

 considerable thickness, and extending over a large district of 

 country, in the states of New York and New Jersey. 



In a sample of this phosphorite from New Jersey I found 

 25*3 per cent, of phosphoric acid, equal to 52 per cent, of bone- 

 earth phosphate, with a large proportion of fluoride of calcium, 

 and 20 per cent, of quartz sand. I have also examined a sample 

 from the state of New York, presented to the Society by Mr. 

 B. P. Johnson, of New York. Many pounds of the material 

 were broken up, so as to ensure an average result, which was as 

 follows : — 



Bituminous matter and water expelled at a red heat 0*69 

 Substances insoluble in acid, chiefly quartz sand . 16*79 

 Silica (soluble in acids) . . , . .0*65 

 Phosphoric acid, equal to 62"27 bone-earth phosphate 30 * 20t 

 Lime 40-10 



* Journal of the Royal Agricultural Society, vol. v., part ii., p. 414. Dr. Daubeny, 

 however, expressly states, that the portion subjected to analysis was selected for its 

 apparent purity and freedom from admixture with the less phosphoric materials of the 

 rock, so lhat practical average would probably give us a much lower percentage of 

 phosphoric acid. 



•j- The mean of four determinations made by different methods : — ■ 

 1st determination gave . . 29-50 

 2nd ,, . . 30-33 



3rd . . 29-77 



4th . . 31-23 



mean 30*20. 



