The Canadian Horticulturist. 305 



DISSOLVED BONES. 



R. AITKIN thus writes of dissolved bones in the North 

 British Agriculturist : Bones contain about half their 

 weight of phosphate of lime, the other half consists 

 chiefly of organic matter. The phosphate of lime in 

 bones is what is called insoluble phosphate, that is to say, 

 a combination of phosphoric acid with as much lime as 

 they can unite with. One-third or two-thirds of the lime 

 can, however, be taken away and still leave definite compounds. When two- 

 thirds of the lime has been taken away, the compound formed is soluble in 

 water and is called soluble phosphate of lime. The object of adding sulphuric 

 acid to bone phosphate is to remove two-thirds of the lime by converting it into 

 sulphate of lime, just as in the case of superphosphate, which is a mixture of 

 soluble phosphate and lime and sulphate of lime. 



In dissolving bones, however, it is found that if enough of acid is added to 

 convert all the phosphates into the soluble form, the whole is converted into a 

 liquid mass, which refuses to dry up and is unfit for use as manure. This is 

 owing to the organic matter in the bones. There is therefore a practical limit 

 set to the proportion of soluble phosphate which dissolved bones can maintain. 

 As a rule, in the case of pure dissolved bones, not more than half the phosphate 

 is present in the soluble form. The usual practice of manufacturers of pure dis- 

 solved bones is to add more acid than is necessary, and to dry up the product 

 with fine bone meal, and, by careful mixing and somewhat laborious treatment, 

 produce a sowable manure. 



Other things besides fine bone meal are often used as dryers. Steamed 

 bone flour dries more effectively than bone meal, but if it is used to any great 

 extent the product will be somewhat high in phosphate and somewhat low in 

 ammonia. Bone ash is found to be a still more absorbent substance, and it is 

 used much to dry up dissolved bones. Bone ash, however, contains no nitro- 

 genous matter, and is very rich in phosphate, and therefore when it is used the 

 product is high in phosphate and correspondingly low in ammonia. Bone ash 

 is not bones, it is simply impure phosphate of lime derived from bones. The 

 same may be said of bone char, which is frequently used as a dryer, and which 

 gives the black color to many manures sold as pure dissolved bones. 



In England there is scarcely to be found a manure sold under the name of 

 dissolved bones which is a genuine article. A great proportion of them contains 

 no bone material at all, and the term dissolved bone is really a conventional 

 name applied to compound manures consisting of any kind of mixture of phos- 

 phate and nitrogenous materials which can be dissolved with or without an 

 admixture of bone. 



