186 CHEMICAL MANUEES. 



The efficiency of bone dust as manure has been the subject of 

 many discussions. P. Wacjner and Mercker seem to have misunder- 

 stood its fertihzing value, whilst other experimentalists have obtained 

 excellent results. According to recent experiments, it is recognized 

 that the efficacy of bone dust was perceptibh' increased by an 

 addition of solvents (? conversion into vitriolized bones) ; nitrification 

 bacteria likewise intervene. A small quantity of the solvent (sul- 

 phuric acid) suffices to give to bone dust a remarkable activity, as 

 experiments on this point testify. This agent has the effect of 

 disintegrating the bone dust, and rendering it soluble in citrate. 

 Stoved bones, non-fat extracted nor degelatinized, do not dissolve in 

 a satisfactory manner. The organic matter of such bone dusts is 

 transformed into a gluev matter verv difficult to drv. 



Classificatioji of Bone Dust. — J. Konig has proposed the follow- 

 ing classification of bone dusts : — 



1. Normal Bone Dusts, or Bone Dust No. 0. — Those bone dusts 

 which are made from bones which have not undergone any treat- 

 ment for the extraction of gelatine, and containing 4 to 5" 3 per cent 

 of nitrogen and 19 to 22 pei' cent of phosphoric acid, in which, more- 

 over, after deduction of the matter extractable by chloroform is as 

 1 : 4 to 5'5. 



2. Bone Dusts {without any other designation). — Those bone- 

 dusts which contain 3 to 1 per cent nitrogen and 21 to 25 per cent of 

 phosphoric acid, and in which after deduction of the matter extract- 

 able by chloroform, the ratio of the nitrogen to the phosphoric acid 

 is 1 : 5-5 to 8-5. 



3. Degelatinized Bone Dusts. — Those which contain 1 to 3 per 

 cent of nitrogen and 24 to 30 per cent of phosphoric acid, and im 

 which after deduction of the matter extractable by chloroform, the 

 ratio of the nitrogen to the phosphoric ac:d is 1 : 8'5 to 30. 



To these kinds of bone dusts must be added the bone dust made 

 in some countries from raw bones. However, there is sometimes 

 sold as raw bone dust the waste from bone-black making after the ex- 

 traction of the fat bv benzine. Nothing should be designated as- 

 raw bone dust unless actually made from raw bones. [The bone- 

 black factories sieve the bone dust from the meal or granules before 

 charring the bones, as the dust is not so efficacious as a decolorizer 

 as the granules. — Te.] 



4. Mixed Manure Dusts. — The manure dusts which after deduc- 

 tion of the matter extractable by chloroform containing 1 per cent 

 of nitrogen as ossein, and in which the ratio of nitrogen to phos- 

 phoric acid is from 1 : 30, should not be designated as hone dusts, 

 but as 7nixed manure dusts. 



Meat Dust {Meat Meal). — An exception to this rule is formed 

 by the manure prepared in the manufacture of meat extract, and 

 which ought to be designated as meat dust (meat mealj, which suffi- 



