CHEMISTRY APPLIED TO THE ARTS. 



white substance, a mixture of palmitin and stearin. 

 The most important vegetable non-drying oils are : 

 Olive-oil, from the fruit of the olive (Olea Europad). 

 Almond-oil, from the fruit of Amygdalus com- 

 tnunis, is obtained by pressure both from the sweet 

 and from the bitter almond, and must be carefully 

 distinguished from the ' oil of bitter almonds/ an 

 entirely different substance (see CHEMISTRY) ; it 

 consists of almost pure olein. Rape-oil, or colza-oil, 

 from the seeds of Brassica campestris : this oil 

 contains very little palmitin or stearin ; it is chiefly 

 used for burning, and is purified by the action of 

 a little strong sulphuric acid, which chars the 

 impurities, mainly fragments of vegetable tissue. 

 Mustard-oil (not to be confounded with the vola- 

 tile oil of mustard, see CHEMISTRY) is obtained by 

 pressure both from the white and from the black 

 mustard (Sinapis alba etnigrd] ; it is a rather thick 

 yellow oil. Palm-oil, from the fruit of Avoir a 

 Elais or Elais Guianensis, is a yellows/a/, fusing 

 at about 80 F. and therefore usually solid in this 

 country : it consists almost entirely of a mixture 

 of olein and palmitin. To remove the yellow 

 colour, it is first melted over water, the solid im- 

 purities (fragments of the husk of the fruit) allowed 

 to settle, and then the clear oil heated nearly to its 

 boiling-point in a current of air. Coco-nut butter 

 is obtained from the coco-nut, the fruit of Cocos 

 nucifera, Cocos butyracea, &c. : it is white and soft, 

 fuses at about 68 F. and consists of olein, pal- 

 mitin, and the glycerides of lauric acid (C 12 H 24 O ? ) 

 and of an acid named cocinic acid, the composi- 

 tion of which has not been exactly ascertained. 



The ANIMAL FATS AND OILS resemble in con- 

 stitution and general character the non-drying 

 vegetable oils. They consist almost entirely of mix- 

 tures of olein, palmitin, and stearin ; the oils and 

 more fusible fats containing most olein, the harder 

 fats most stearin. The most important are : 

 Oils. Neatsfoot-oil, much used by watchmakers, 

 is prepared by placing the bones of the feet of 

 oxen, carefully cleaned from the hoofs and from 

 adhering fat and skin, and well broken up, in a 

 gently warmed oven, when the oil flows out, and 

 is purified by allowing the impurities to settle in 

 a closed glass vessel. It remains solid at the 

 freezing-point of water, and does not readily be- 

 come rancid. Fish-oil, or train-oil, is obtained 

 from various large sea-animals whales, seals, 

 dogfish. It consists chiefly of olein and palmitin 

 with some stearin. It is used as a lubricant, and 

 for smearing leather (see p. 347), also (as indeed 

 are all the cheaper oils and fats) for making soap. 

 Cod-liver oil is obtained from the liver of the 

 common cod (Gadus morrhud) and the ling 

 (Gadus molvd), also from the dorse (Gadus cella- 

 rius) and coal-fish (Gadus carbonarius.) It is 

 distinguished as 'brown,' 'pale,' and 'yellow' oil, 

 according to its colour, which varies according to 

 the mode of extraction. It consists chiefly of 

 olein, palmitin, and stearin, with small quantities 

 of free butyric and acetic acids, and a peculiar 

 substance called ' gaduin.' Its efficacy as a medi- 

 cine has been ascribed to small quantities of 

 iodine and bromine, but it is more probable that it 

 acts merely as a fattening food. 



The solid animal fats are, like the animal oils, 

 present in the living animal in the liquid state, 

 but have a fusing-point so high that they are 

 solid at the ordinary temperature of the air. They 

 are obtained by boiling the tissues containing them 



with water, when the fused fat rises to the surface,, 

 and is thus separated from the fibrous connective 

 tissue with which it was mixed. They differ from 

 one another chiefly in the proportions of stearin,, 

 palmitin, and olein, which they contain. The 

 olein can be to a great extent removed by pressure 

 at a low temperature ; what is left as a solid after 

 thus squeezing out the olein, may be further 

 separated into stearin, and a substance, fusing; 

 at a lower temperature, called ' margarine.' This 

 was formerly supposed to be a distinct fatty sub- 

 stance, the glyceride of 'margaric acid,' but has- 

 been proved by Heintz to be a mixture, or perhaps 

 a compound, of stearin and palmitin. 



As an appendix to the animal fats and oils, we 

 may mention two important substances which re- 

 semble them in many respects, but which are not 

 usually classed along with them, as they are not 

 ' glycerides.' These are ' spermaceti ' and ' bees- 

 wax.' Spermaceti is a fatty substance found in 

 cavities in the head of the sperm-whale (Physeter 

 macrocephalus\ and in some other allied whales. 

 When freed from adherent sperm-oil, it is a colour- 

 less, inodorous substance, fusing at from 100 to- 

 1 15 F. By dissolving in alcohol, and crystallising, 

 pure ' cetin' can be obtained, fusing at 122 F. It 

 is a compound ether or 'ester' (see CHEMISTRY) 

 of palmitic acid and cetylic alcohol (CjgH^O),. 

 and stands to cetylic alcohol in the same relation 

 as palmitin does to glycerine. 



Beeswax is a yellowish substance secreted by 

 bees, and used by them in the formation of their 

 cells. When exposed in thin layers to air and 

 sunlight, it is bleached, and becomes white. It is 

 a mixture of three distinct substances, which can 

 be separated from one another by means of 

 alcohol : I. Myricin, insoluble in boiling alcohol ; 

 2. Cerotic acid, soluble in boiling alcohol, but 

 crystallising out on cooling ; and 3. Cerolein r 

 which remains dissolved in the alcohol after it 

 has cooled. Myricin is a compound ether of 

 palmitic acid and melissic or myricylic alcohol 

 (C^H^O). Cerotic acid has the composition 

 CzjH^O^. Cerolein is a soft substance, fusing 

 at about 84 F. the constitution of which has not 

 been exactly made out ; wax contains only 4 or 5 

 per cent of it 



SOAP 



is formed along with glycerine when a fat 

 or fatty oil is boiled with a fixed caustic alkali, 

 such as caustic potash or caustic soda. Soap, 

 therefore, consists (see CHEMISTRY) of salts of 

 the oily and fatty acids, with potash or soda as 

 a base. The soap can be separated from the 

 watery liquid by the addition of common salt- 

 The soap being insoluble in salt water, separates 

 as a curd, while the glycerine remains dissolved 

 in the salt water. 



Soaps may be classified according to the base 

 present, as ' hard soaps,' containing soda ; and 

 'soft soaps,' containing potash. They may be 

 further classified according to the acids or mixture 

 of acids from which they are derived. Thus,, 

 there are oleic soaps (oleates of potash or soda), 

 palmitic soaps (palmitates of potash or soda), 

 and stearic soaps (stearates of potash or soda). 

 Further, many of the soaps of commerce con- 

 tain various ingredients mixed with them, either 

 to increase their detergent action, or as mere 



Ml 



