216 



On Superphospliate of Lime. 



the phosphate^ which will eventually come into operation as a 

 manure, although at a later period of the growth of the plant. 



Neither does it appear that any slight error or understate- 

 ment of the percentage of phosphate of lime in raw bones will 

 make the difference to which we are calling attention. Know- 

 ing the composition of the bones and the quantity of acid em- 

 ployed, we may readily calculate what would be the composition 

 of a mixture such as we have described after it had dried up to 

 a given extent. My experience of superphosphate of lime, as it 

 occurs in the market, would induce me to fix the proportion of 

 moisture at about 10 per cent., and, if some specimens exceed 

 this proportion, the greater number of well-made samples fall 

 short of it. The mixture of 100 lbs. of raw bones and 29 lbs. of 

 oil of vitriol would, after drying up, give a product having the 

 following composition in 100 parts :- — 



Moisture . . . .10 

 Animal matter and fat . . 27 

 Hydrated sulphate of lime 

 (gypsum) . . . .39 



j Equal to 35 parts of bone- 

 Bi-phosphate of lime, soluble . 24-! earth phosphate rendered 



I soluble. 



100 



The animal matter (gelatine), being about 21 per cent., would 

 furnish I J lb. of nitrogen, equal to rather more than 1+ lb. of 

 ammonia. 



In the above statements no neutral or insoluble phosphate is 

 meniioned, because it is supposed to be entirely converted into 

 bi-phosphate. We must repeat that this is practically impossible ; 

 the manufacturer will either fall somewhat short of the entire 

 decomposition of the phosphate, or he will go beyond it, setting 

 phosphoric acid free, which to the consumer is by no means an 

 objection. But it is certainly an object, especially when the 

 phosphate employed is of mineral origin^ to exceed rather than 

 fall short of the mark, so as to leave none of the insoluble phos- 

 phate unacted on. 



1 pass on now to consider the manufacture of this manure 

 from boiled bones, in which state probably by far the larger 

 proportion of them are used. 



When bones are boiled their fat is separated, and a good 

 deal of the gelatine or glue is at the same time extracted. The 

 fat separates pretty readily, but the bones require lengthened 

 boiling to extract much of the gelatine. They will be more or 

 less altered, therefore, according to the purpose with which they 

 have been boiled. If the fat alone has been taken out, the 

 only change necessary in the formula given for the raw bones 



