OILS. 



gen, and having an affinity for that 

 element, whereby they become rancid 

 or are converted into resins. They 

 are compounds of the margaric, oleic, 

 or stearic acids, with glycerine, and 

 owe their value not only to their pe- 

 culiar properties, but to the soaps 

 and liniments they form with alkaline 

 substances. They are in all respects 

 fluid fats of vegetable and animal ori- 

 gin, agreeing very closely in struc- 

 ture. Thus per cent., 



Carbon. Hydrogen. Ojygen. 

 Olive oil consists of 77-2 13'3 9'5 



Spermaceti " 780 IIS 102 



Oils are divided into expressed or 

 fixed oils, W'hich are also subdivided 

 into drying oils and connnon oils, and 

 into distilled or essential oils. The 

 common fat oils are like almond and 

 olive, bland, preserving their flavour 

 for a long time, but becoming ran- 

 cid ; palm oil is solid. The drying 

 oils are like linseed, hemp seed, nut 

 oil ; they attract oxygen readily from 

 the air, evolving heat, and become 

 solid. The essential oils impart to 

 flowers and aromatic bodies their 

 odour ; they are very volatile, and are 

 obtained by distilling the leaves or 

 flowers with water. All vegetables 

 contain a proportion of oil of some of 

 these varieties, which may be obtain- 

 ed by digesting them in ether and al- 

 cohol ; it is, however, frequently be- 

 low one per cent., while in other 

 cases, as the nut, it is more than sixty 

 per cent. In provender, the fattening 

 quality is closely related to the per 

 centage of common oil. The follow- 

 ing table contains the best informa- 

 tion on this topic : 



. . 8 to 12 per ceut. 

 . . 0-8 



Common maize 



Rice . . . . 



Oats . . . . 



Ditto . . . . 



Rye . , . . 



Rye flour . . 



Hard wheat . . 

 VV'lieat flour 



Ditto . . . . 



Fine bran . . 



Coarse bran . . 



Dry clover . . 



Dry lucern . . 

 Meadow hay 



Oat straw . . 



Bean meal . . 



Beans . . . . 



llaricoll . . . 



55 

 3.3 



1-8 

 35 

 2-6 

 2 1 

 14 

 4-8 

 52 

 40 

 35 

 3-8 

 51 

 21 

 2-0 

 30 



M. Payen found that the oil was 

 everywhere present in the seeds of 

 gramineous plants. The embryo 

 contains much, the husk less, the 

 farinaceous portion still less ; but 

 maize and oil-cake contain about 9 

 per cent., whence the universally ad- 

 mitted superior fattening power of 

 these two articles. 



The crops enumerated in the fol- 

 lowing table are those principally 

 raised for oil (the bene might be add- 

 ed) : it is from Boussingault : 



A few oils, as the castor and caje- 

 put, are eminently medicinal, al- 

 though expressed ; this arises from 

 the presence of peculiar principles in 

 them. Camphor is by some wTiters 

 regarded as a concrete volatile oil. 



The process for procuring express- 

 ed oils is either conducted with or 

 without heat ; where no heat is em- 

 ployed, less, but a superior kind is ob- 

 tained, which resists the action of air 

 longer, and is of a more delicate fla- 

 vour. For virgin oils the seeds are 

 first crushed, either between iron rol- 

 lers, in mortars, or in an edge mill, re- 

 sembling the bark mill (see Oil Mill) ; 

 the crushed mass is then enclosed in 

 strong hempen or woollen bags, and 

 this often in another of horse hair, 

 and subjected to the pressure of a 

 screw, placed in a hydraulic oil mill, 

 or merely into press boxes of stout 

 materials, and pressed by driving 

 wedges perpendicularly between the 

 sides of the box and bags. The hy- 



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