1921.] Wright.—Chemical Technology of Meat Industry. 105 
The cooked bones are easily broken up. It is not customary to dry 
them in a mechanical dryer, but to leave them to dry spontaneously in a 
“ den.” They are thereafter crushed finely in a grinding-mill, and, as 
bonedust, used as a fertilizer. 
The composition of bonedust varies greatly within the following limits : 
Moisture, 5 to 10 per cent. ; tricalcic phosphate, 45 to 65 per cent. ; 
nitrogen, 1 to 4-75 per cent. (= ammonia, 1-22 to 5*78 per cent.). 
Hoofs and Horns. (8, 25.) 
Hoofs and horns make upon treatment a material which is useful for 
fertilizer purposes. In general these materials are rendered in connection 
with the bones of the head, or with the shin or shank bones of the feet, 
but they are removed from the other material and crushed separately. 
This material has a high content of nitrogen, and may be used in sup¬ 
plementing the nitrogen content of the other materials used in mixed 
fertilizers. 
The composition of hoof-and-hom meal varies somewhat, but usually 
lies within the following limits : Moisture, 2 to 5 per cent. ; nitrogen, 12 to 
14 per cent. (— ammonia, 14-6 to 17 per cent.). 
Compound Fertilizers. (25, 27, 31, 32, 33.) 
In connection with the frozen-meat industry the utilization of the 
materials recovered in the rendering of the animal-tissues—namely, tankage, 
concentrated tankage, bonedust, dried blood, and hoof-and-horn meal—is 
further extended by their application in connection with mixed or com¬ 
pound fertilizers. 
The materials used, in addition to those manufactured by the frozen- 
meat fertilizer plants, are guanos and mineral phosphates of various grades,, 
superphosphate, sulphate of ammonia, cyanamide, nitrate of soda, potash 
salts, and diluents. 
In practice cyanamide should not be used in conjunction with sulphate 
of ammonia or animal ammoniates ; nitrate of soda should not be used 
in conjunction with superphosphate ; if it is wished to maintain the soluble 
phosphate of the superphosphate, diluents or other materials containing 
lime or carbonate of lime should not be used. 
Each firm, of course, possesses individual ideas regarding its proprietary 
brands of mixed fertilizers, and, while no discussion concerning the value 
of the different products is desirable, it may be stated that, in general, the 
tendency of the manufacturer and mixer has been to supply the soil and 
plant needs which experiment and soil-survey throughout New Zealand 
have established under the direction of the Chemist of the Agriculture 
Department—namely, that the immediate requirement of the average 
New Zealand soil is phosphatic. 
It mav thus seem that the utilization of the animal ammoniates manu- 
t/ 
factured in connection with the frozen-meat industry is without justifi¬ 
cation in their application to New Zealand soils ; but consideration will 
show that such is not the case. The soil is not a dead, inert substance, 
but a living, active medium in which products are transformed by the 
aid of bacteria into substances suitable for plant-food. From the stand¬ 
point of soil-fertility in its more permanent relations the question of 
bacterial activity and its proper encouragement gives promise of larger 
