184: CHEMICAL MANUEES. 



than the fat from ordinary country bones (? rag bones). It is puri- 

 fied by treatment in a lead-lined pan, by water acidulated with 

 sulphuric acid, of which an excess must not be used. The fat and 

 the acidulated water are then heated by a peiforated steam coil, 

 which beats the two up together. After some time the tallow shows 

 clear and no turbidity in the spoon. The steam is turned otf and 

 the whole allowed to stand. The mixture of tallow, gelatine, 

 carboQ and phosphate of lime, and fatty acids combined with lime 

 is destroyed, the gelatine is dissolved and oxidized by the acids, and 

 the lime is precipitated as sulphate of lime with various impurities. 

 After sufficient resting, the layer of fat is separated by means of a 

 pipe hinged to the draw-off tap.^ This pipe enables the pure fatty 

 layer to be run off" and to reject the water and sulphate of lime. 

 The purified grease falls into a wooden vat lined with lead, where 

 it is washed several times with boiling or simply tepid water. After 

 which it is let stand and drawn oft' as before into casks for use in 

 soap works or candle w^orks. 



Bone fat is often bleached as follows : — - 



To the melted fat mixed w4th half its volume of water, 2-5 per 

 cent of chlorate of potash is added and enough hydrochloric acid to 

 decompose the whole of the chlorate. An excess of this acid is 

 added to neutralize calcareous compounds. The tallow is purified 

 and whitened with 2-5 per cent of chlorate and a semi-tint obtained ; 

 with 5 per cent of chlorate a whiteness of the tallow is obtained 

 analogous to that of lard. It is w^ashed several times with water, 

 until the wash water is free from chlorine, which is recognized by 

 iodized paper. Bleaching by sunlight is equally energetic. The fat 

 must be run into shallow vats which are exposed to the light. 

 x\gitatiou in presence of ozonized air also constitutes a method of 

 bleaching. At the normal temperature, bone tallow is soft, unc- 

 tuous, and does not rancidity easily. Although insoluble in water, 

 like all fats it contains about 2 per cent of water, which it is im- 

 possible to ehminate even by heating it to 100^ C. To obtain it in 



^ Bone fat is rather too viscous and easily cooled to be readily syphoned. 

 It is transferred from the refining pan to the wash pan by short-handled ladles 

 or dippers, and filled from the wash tank into barrels standing alongside by the 

 same dippers. After the bone fat has cooled and set the casks are headed up by 

 a coop?r or handy man. — Tr. 



2 The author does not differentiate between the bleaching of white bone 

 fat got by boiling of fresh bones and of brown bone fat got by extracting 

 rag bones by benzine. The best results the translator got with chlorine as 

 a bleaching agent of brown bone fat, was a canary colour. Brown bone fat takes 

 up tons of water to form a white emulsion, but deprived of the emulsive water, it 

 is a long way oft' white. Sulphurous acid is said to give good results, and 

 possibly in soap-making it could very well be bleached by hydrosulphite or 

 " blankit " in the soap-pan. But possibly it is impossible to eliminate the 

 fusty smell of brown bone fat even from soap made frcm it. — Tn. 



