448 OILS 



grows in Malabar. It is obtained by boiling the fruit with water, and collecting the 

 fat which rises to the surface. It is white, greasy to the touch, and of an agreeable 

 odour. Its fusing-point is at about 95 ; its specific gravity at 59 is 0*926, and at 

 95, 0-8965. It answers well for the manufacture of soap and candles ; but is little 

 known in this country. 



Spindle~tree Oil. The oil of the spindle-tree (Euonymus Europceus}, is yellowish, 

 rather thick, with the odour of colza oil, of a bitter and acrid taste. It is solid at 

 5 Fahr. 



Butter of Kutmegs. This is commonly known in the shops as expressed oil of mace, 

 and is prepared by beating the nutmegs to a paste, placing them in a bag and ex- 

 posing them to steam, and afterwards pressing between heated plates. It is imported 

 in oblong cakes (covered by some leaves), which have the shape of common bricks, 

 only smaller. It is of an orange colour, firm consistence, fragrant odour, like that of 

 nutmegs. The genuine article may be known by being soluble in four times its 

 weight of boiling alcohol, or half that quantity of boiling ether. Its principal use is 

 in medicine. It must not be confounded with essential oil of mace. 



THE DBYINQ OILS. 



Linseed Oil. The oil is obtained by expression from the seeds of the common 

 flax (Linum usitatissimum), either with or without the aid of heat ; the latter, being 

 known as cold-drawn linseed oil, is better than that expressed by heat. 



Linseed oil is easily saponified, yielding a mixture of oleate and margarate of the 

 alkali, and a large quantity of glycerine. 



It is acted on rapidly by nitric acid, producing margaric acid, pimelic acid, and 

 some oxalic acid. 



Chlorine and bromine act on it, yielding thick, coloured products : when linseed 

 oil is heated in a retort it gives off, before entering into ebullititin, large quantities 

 of white vapours, which condense to a limpid, colourless oil, possessing the odour of 

 new bread. As soon as the ebullition commences these vapours cease ; the oil froths 

 up, and at length there is left a thick gelatinous residue, very much resembling caout- 

 chouc. 



The principal use of linseed oil is in making paints and varnishes. It attracts 

 oxygen rapidly from the air and solidifies, and this property is what renders it so 

 valuable for these purposes : it is the most useful of all the drying oils. The small 

 quantities of vegetable-albumen and mucilage which the oil naturally contains appear, 

 according to Liebig, to impair to a certain extent its drying qualities, and the real 

 object which is obtained by boiling these oils with litharge, or acetate of lead and 

 litharge, is the removal of these substances ; the oil then being brought more directly 

 in contact with the oxygen of the atmosphere, dries up more rapidly. It was pre- 

 viously thought that some of the litharge was reduced to metallic lead, oxidising at 

 the same time some of the linoleine ; but Liebig's opinion seems to be more likely fo 

 be correct. The boiling of the oil requires some little care. A few hundredths of 

 litharge is added to the oil, or some use acetate of lead and litharge, and, as before 

 stated, about an eighth part of resin ; this is boiled with the oil, the scum removed as 

 it forms, and, when the oil has acquired a reddish colour, the source of heat is re- 

 moved, and the oil allowed to clarify by repose. Liebig thinks heat is not necessary, 

 and his process for treating the drying oils, in order to increase their siccative pro- 

 perties, has already been mentioned. According to MM. E. Barruel and Jean, the 

 resinification of the drying oils may be effected by the smallest quantities of certain 

 substances, which would act in the manner of ferments. The borate of manganese 

 acts in this way ; a thousandth part of this salt being sufficient to determine the rapid 

 desiccation of these oils. 



Linseed oil is used in the manufacture of printer's ink. Being heated in a vessel 

 until it takes fire, it is allowed to burn some time, then it is tightly covered ; and 

 subsequently mixed with about one-sixth of its weight of lamp-black. 



The thin, gummed silks receive the last of their many layers with boiled linseed- 

 oil ; it is also used for leather-varnishes and for oil-cloths. 



The residue, after the expression of the oil from the seeds, is called oil-cake, and is 

 sold for feeding cattle ; that obtained from the English linseed is the best. 



Walnut Oil. This is obtained by expression from the, ordinary walnuts deprived 

 previously of their skin, which are the produce of a tree (Juglaiis regia) which is a 

 native of Persia, but cultivated in this country for the sake of the nuts. 



When recently prepared it is of a greenish colour, but by .age becomes a pale 

 yellow. According to M. Saussuro its specific gravity at 53'6 Fahr. is 0-9283, 

 and at 201 Fahr., 0-871. It has no odour, but an agreeable taste. At 5 Falir. 

 it thicken?, and at 17-5Fahr. it forms a whitish mass. The nuts yield about 50 



