300 OILS AND FATS. 



fluid is made. Add one pint of finely minced caoutchouc to fifty pints 

 of rape oil, and heat until the mixture is complete. A very unctuous 

 oil is thus formed, which remains fluid at freezing temperature, and does 

 not clog the machines, but facilitates the motion of their parts. 



Heydenreick proposes (' Journ. de Connais. Utiles,' 1849) to distin- 

 guish fat oils from each other by their odour when warmed, their colour 

 by contact with oil of vitriol, and their specific gravities. By the first 

 process the oil is heated in a porcelain capsule over a spirit-lamp, when 

 the peculiar volatile odour of fish, linseed, and other oils may be 

 detected, especially if compared in the same way with the unadulterated 

 oils. For the acid test, from ten to fifteen drops of the oil are dropped 

 upon a piece of glass, underlaid by white paper, and a drop of oil of 

 vitriol is brought in contact with it by a glass rod. If it be rape-oil, 

 a greenish-blue circle is formed around and at a short distance from the 

 drop, while light yellowish-brown strias form towards the centre. The 

 same takes place with oil of black mustard, but from twenty-five to 

 thirty drops of the oil are recmired. With whale oil, the colour is red- 

 dish, after twelve to fifteen minutes violet on the edge, and in two hours 

 violet throughout. Olive oil gives a pale-yellow, passing into greenish- 

 yellow. Linseed oil is at first dark reddish brown, and then black. 



The more solid fat, stearin, is separated from the more fluid olein by 

 pressure, to make stearin-candles, or, the fats being decomposed, the 

 more solid stearic acid is separated from buttery or fluid acids, to make 

 stearic acid lights. Under this head we may embrace spermaceti and 

 wax. There is but little novelty offered on any of these points. 



To separate the solid from the more fluid fat in palm oil, lard, &c, 

 the fats are granulated and pressed cold in bags by a powerful hydraulic 

 press, the olein which flows out being used for soap. The contents of 

 the bags being again granulated, and pressed between warm plates of 

 iron, the balance of the olein, with some margarin and stearin, is then 

 removed. To remove colour from the stearin thus obtained, it is fused 

 with a very little nitric acid. To remove still further all the olein, 

 Morfit proposed mixing it with a little oil of turpentine, and then 

 pressing. See Morfit's ' Chemistry Applied to the Manufacture of Soap 

 and Candles.' According to Heintz (Ber. d. Berl. Acad.), stearin from 

 mutton suet becomes transparent at 124° to 126°, but does not fuse 

 before 144°. 



A process is described in the ' Rep. Pat. Inv.' Oct. 1850, for mixing 

 some twenty to thirty per cent, of rosin with fatty bodies in the melted 

 state, by adding sulphuric acid gradually, heating it from twelve to 

 eighteen hours, so as to evolve sulphurous acid, and then submitting the 

 dark-brown crystalline solid to distillation by heated steam. The solid 

 and oily portions are then separated by pressure. 



To test for the presence of stearic acid, Geith pours over two drachms 

 of wax, one ounce of lime-water, diluted with one ounce of water. If 

 the acid be present, the liquid loses its alkalinity, and remains clear. 



