Solubility of Phosphatic Materials. 
1D3 
acid li(jui(l, csscMitially a solution of bone-phosphate in hydro- 
chloric acid, are obtained. By adding slaked lime or carbonate 
of soda until the free acid is neutralised, the phosphates fall 
down as a white voluminous precipitate, which after subsidence 
may be collected, partially washed, and dried on a hot plate. 
When carefully prepared in this way, precipitated bone-phos- 
phates constitute a very valuable fertilising material, which is 
readily assimilated by plants. 
A reference to experiments given in preceding pages will show 
that, in a precipitated state, phosphate of lime is far more easily 
soluble in water, and more efficacious as a manuring agent than 
in the shape of phosphatic minerals, bone-ash, or even fine bone- 
dust. 
When moderate care and skill are employed in the manufacture 
of precipitated phosphates, an exceedingly light, dry, and very 
valuable white powdery substance containing from 78 to 80 per 
cent, of pure tri basic phosphate of lime can be obtained. 
Generally, however, workmen add more lime to the acid 
liquid than is necessary to precipitate the phosphates, and the 
excess of lime falls down with the precipitate and afterwards 
gets changed into insoluble carbonate of lime, which remains 
mechanically mixed with the phosphates. 
The addition of slaked lime to the acid liquid, I need hardly 
say, produces chloride of calcium, which remains in solution. 
The liquid containing this very deliquescent salt is seldom removed 
as perfectly as it might be from the precipitated phosphates. 
Prepared on a manufacturing scale the bone precipitate generally 
contains some carbonate of lime with more or less chloride of 
calcium, moisture, and water of combination. It is sold in com- 
merce as bone-flour, and varies much in composition, and con- 
sequently in value, as will be seen by glancing at the subjoined 
analysis ; — 
Composition of two samples of Bone-flour {precipitated Bone-phosphates). 
I. II. 
Moisture and water of combiuatiou 30'20 .... 22'51 
•Phosphoric acid 23-83 .... 3050 
Lime 34-52 .... 40-65 
Magnesia, chlorine, &c 9-92 .... 6-15 
Sand 1-53 .... -19 
100-00 100-00 
*Equal to tribasic phosphate of lime (bone-earth) 52"04: 66*58 
In a third very inferior sample I determined separately- 
chlorine, carbonic acid, phosphoric acid, lime, &c. Uniting the 
constituents found in the compound, its composition may be 
stated as follows : — 
VOL. IV. — S. S. O 
