188 CHEMICAL MAXUEES. 



or if its percentage of nitrogen has been artificially increased, as a 

 mixture of normal bone dust, phosphorite and of dried blood. All 

 the phosphoric acid in excess above the ratio of the proportion of 

 ossein nitrogen to phosphoric acid should be regarded as raw phos- 

 phate, and of no value to the farmer. 



But these sorts of bone dusts yield excellent results if converted 

 into superphosphates. In fact, if all the phosphoric acid be dis- 

 solved, the latter has no need of ossein in the soil ; the bone dust 

 so treated constitute-s a nitrogenized superphosphate. The manu- 

 facture of bone superphosphate (pure dissolved bones) is very simple.^ 

 The bones, previously crushed and degreased, are reduced to powder 



^ The author does not quite do justice to the grave technical difficulties 

 which beset the making ot pure dissolved bones. It is almost an impos- 

 sible task. The difficulties begin at the outset. First of all, working with 

 a mixer that will easily make 2^ tons of mineral superphosphate at a mix- 

 ing, the charge must be reduced to ton mixings, and with certain intractable 

 bone meals to | ton mixings. The reason is that the interaction between 

 the acid and the bone dust is more energetic than in the case of mineral 

 phosphate, and owing to the r ipid formation of sulphate of lime the mixer tends 

 to set. This perforce leads to the use of water to get the charge out of ihe 

 mixer. In the " den "' the finished mass looks like dirty porridge, white inside 

 but brown on the surface where exposed to the air. The only way to dry it is 

 to cut it into pieces with the shovel and sprinkle it with bone meal, dry in an 

 oven, and then try to coax it through a wide-meshed screen with more bone 

 meal and then through a finer screen again with more bone meal. Bone super- 

 phosphate, pure dissolved bones, vitriolized bones, will never dry in the heap. 

 But the translator found it to dry well in the sun by turning the pieces over and 

 sprinkling with bone meal. It will thus be seen that to make pure vitriolized 

 bones is a costly operation and one which in no way pays the conscientious 

 manufacturer who looks askance at any order for it. As to putting bone black 

 up the cups before the bone dust, the only advantage the translator can see is 

 that the bone black is more tractable, but he never found it to have any great 

 drying properties. Bone ash if available would be far less objectionable. For 

 one thing it would not make the manure unsaleable. Farmers when they see 

 a black manure always think of soot, and the translator will always remember 

 the anathemas hurled at him by a farmer whose order for a 37 per cent soluble 

 phosphate he had executed with a bone black superphosphate. A little bone 

 black goes a long way, a- paint manufacturers know, and a farmer decidedly 

 objects to a manure as black as his hat. He can only te t the manure organo- 

 leptically, and he fiatters himself he knows soot when he sees it. But ihen a 

 pure dissolved bone should consist of nothing but raw bone and acid. Strictly 

 speaking, bones tre-ited for their fat or the r gelatine cease to be bones, and 

 their definition must be qualified. As to the addition of nitrate of soda in the 

 mixing, that will give a good deal more than 2 per cent of salt cake in the 

 dissolved bones, and that can only be looked upon as an adulterant. Besides, 

 nearly J cwt. of nitre to the ton of bones would mean that the operation, owing 

 to the fumes, would be insupportable, as the steam rolls off in billows and 

 it only wants nitrous fumes to make the position of the man at the mixer a far 

 from enviable one, especially with a mixer that is open or half open during the 

 mixing process. Again, why should the manure manufacturer lose o=. per ton 

 of bones for which he gets no credit ? All the same, nitrate of soda up the cups 

 will no doubt help the dissolved bone to dry, and as a matter of fact it assists 

 all manure^, but a black draught may gas the man at the cups who cannot well 

 get away from it. A rapid current of warm air is what is required to dry vitriol- 

 ized bones. Diying machines like Figs. 32 and 33 should be etiectual. Stewing 

 in an oven with a poor draught is not at all effectual and chars the manure. — Tk. 



