196 MINERAL MANURES. [ VIII. 



potash and soda). The potash usually contains 60 per cent, 

 carbonate, 10 per cent, sulphate, 10 muriate, and some silicate 

 of potassa. 2. Equal parts of phosphate of lime, potash, and 

 soda. The above mixtures are each fused separately in a re- 

 verberatory. According to the peculiar wants of the soil, the 

 proportions given may be varied, and also different substances 

 added, such as plaster, bones, silicated alkali, ammonia, phos- 

 phate of magnesia. According to Stenhouse, the calcareous 

 phosphate may be obtained from urine, as well as from guano 

 and bones, by adding milk of lime, drawing off the liquid 

 from the deposit, and drying the latter. lOOR) urine yield 

 nearly |ft) of the precipitate, which when dry contains f phos- 

 phoric acid, g lime, &c., and ^ nitrogenous organic matter. 



Analysis of Bone-earth. — Heintz's analyses of bones (Ber- 

 lin. Berichte, 1849) give the following results. 



Human. Sheep. Ox. 



Lime 37.89 37.51 ... 40.00 ... 37.46 



Magnesia 0.57 0.56... 0.74... 0.97 



Phosphoric acid 28.27 28.00 ... 29.64 ... 27.89 



Carbonic " 2.80 2.81 ... 3.08 ... 3.10 



Water, fluorine, and organic 



matter 30.47 31.12 ... 26.54 ... 30.58 



Pliosphates of Lime. — Roesky's experiments (Comptes Ren- 

 dus, xxvi. and Ch. Gaz. vi.) show that the artificial or bone 

 phosphate of lime has the composition 3CaO,P05; that the 

 biphosphate of lime is decomposed by alcohol into a phosphate 

 and free acid ; but the former is not a neutral salt but a new 

 phosphate 3CaO,2P03,4HO. 



8oluhility of Pliosphates. — According to Liebig, 1 litre of 

 water saturated with carbonic acid, dissolves 0.6626 grm. of 

 bone-earth, of which 0.500 grm. is deposited by boiling. (Ann. 

 der Chem. und Pharm. Ixi.) According to Lassaigne, water 

 with its own volume of carbonic acid, dissolves in the course 

 of 12 hours, at the temperature of 50°, 0.00075 of artificial 

 l)asic phosphate of lime, 0.000166 from fresh bones, and 

 0.0003 from bones that had been buried for 20 years. He 



