VOLATILE OILS.] 



CHEMISTRY. 



419 



Almond oil is afforded by the almond tree, the nuts of 

 which give the oil, on the kernels being crushed or 

 pressed. 



Linseed oil is afforded by the seeds of the flax plant ; 

 and the seeds of the Indian hemp also contain abundance 

 of oil. The cake left after the extraction of oil from 

 linseed, is largely used as food for fattening cattle. 



Rape and Colza oil are the produce of seeds of the 

 ftrasxica family. The latter oil has been much employed 

 of late for lamps. That of the rape-seed is much used 

 for the same purpose, but both require refining from 

 various substances with which they are mixed in the raw 

 state. 



Mut, Poppy, Cotton, Mustard, Sunflower, (fee., oils, are 

 obtained from the seeds of the plants bearing their 

 names, and have different use>, depending on their 

 specific qualities. They are employed in the manufacture 

 of soap, for illuminating and lubricating purposes ; and, 

 generally speaking, the solid refuse left after extracting 

 the oil, may be employed as food for cattle. There are 

 numerous other vegetable fixed oils, to which we need 

 not allude separately. 



VOLATILE OILS. These oils are the produce, in most 

 cases, of the flowers of plants, which owe their fragrance 

 to them. In some cases, however as oil of turpentine 

 the oil is obtained from the wood of a tree. Volatile 

 oils are generally soluble in alcohol, and hence are largely 

 used as perfumes. 



Perfumes have for ages been highly esteemed ; and in 

 the earliest records of biblical and general history, we 

 read of various productions of that class. This will be 

 a matter of no surprise, when we remark that the climate 

 of Greece, Turkey, and Egypt, countries in which the 

 early history of the world is involved, is such as to be 

 most favourable for the production of flowers affording 

 the best perfumes. At the present day, we are indebted 

 to those countries for many of our best essential oils ; 

 and the otto or attar of roses is indigenous to Damascus 

 and its neighbourhood. 



In England many places are devoted to the cultiva- 

 tion of flowers intended for the use of the perfumer. 

 Mitcham and its neighbourhood, and other places in 

 Surrey, are especially noted for the cultivation of Mowers 

 for perfumery and medical uses. In Germany and on 

 the banks of the Rhine, as at Vierlander, t!ie cultivation 

 of flowers is an object of importance to the farmer and 

 landholder. 



There are many ways of obtaining the perfumes con- 

 tained in flowers. Some yield their essential oil readily ; 

 others part with it more slowly. The following methixls 

 may be tried, and they serve as illustrations of the 

 various modes adopted according to circumstances : 



1st. Dip some fine cotton lamp-wick in the purest 

 olive oil, and lay the petals of the flowers on these 

 threads. Place these over each other in layers, and after 

 some time loosen the threads, and soak them in a glass 

 of warm water. The oil will gradually ooze out, and, 

 with the water, may then be transferred to a still. As 

 distillation proceeds, the more volatile oil will separate 

 from the fixed one, and, passing over, may be condensed 

 in the worm, together with a portion of the vapour of 

 water. As the oil and water condense, the two will 

 separate, and the essential oil will float on the water 

 surface, from which it may easily be removed. For this 

 purpose it is better to receive the condensed liquids in a 

 glass vessel, because in that they will be more readily 

 distinguished. 



2nd. The flowers may be rubbed together with dry 

 chalk or loaf sugar in a mortar, and water is then to be 

 added. The mixture, so obtained, is to be transferred 

 to the still, and the usual process of distillation being 

 carried out, the oil is readily separated. The essential 

 oil of lemons is obtained very easily by rubbing the out- 

 side of the peel with loaf sugar, which, on being dis- 

 solved in water in the body of the still, soon yields up 

 the oil by distillation. 



3rd. The leaves of the flowers may be soaked for 

 some time in a strong solution of common salt in water. 

 This extracts the oil, and the liquid can then be distilled. 



4th. But the readiest way in most cases is to steep 

 the flowers for some time in strong spirits of wine. The 

 spirituous solution so obtained is then to be transferred 

 to the body of the still, and the vapour being condensed 

 in the worm, will be found to contain the essential oil 

 in union with the spirit. 



We have already pointed out other properties of essen- 

 tial oils. They consist chiefly of carbon, hydrogen, and 

 oxygen ; but in some nitrogen is found ; and in the oil of 

 the onion, <fec. , sulphur is also present. It will be un- 

 necessary for us to describe such oils as those of roses, 

 lavender, neroli, lemons, bergamot, &C. , as their general 

 qualities are so well known. We shall therefore confine 

 our remarks to the following : 



Turpentine and Camphor. These substances are both 

 the produce of the wood of trees. Oil of turpentine is 

 obtained from the pine, larch, and fir. The tree is 

 "tapped ;" that is, a hole is cut into it a little above the 

 ground, and the resin exudes, and is collected in suitable 

 vessels. The oil is obtained from the crude product by 

 distillation. Its specific gravity is 870 water = 1000, 

 and it is highly inflammable. Common turpentine is an 

 impure form of the liquid. 



Camphor is obtained from a plant, the Laurus Cnm- 

 phora, by distillation of the wood. This well-known 

 substance is highly inflammable, can be sublimed br a 

 moderate heat, is but slightly soluble in water, but 

 readily in alcohol, and has numerous medicinal and other 

 uses. A peculiar acid, the camphoric, is obtained by the 

 action of nitric acid and heat on camphor. A substance 

 resembling camphor may be produced by passing hydro- 

 chloric acid gas through oil of turpentine. 



Cedar and sandal-wood, and valerian root, each afford 

 an essential oil from the solid portion of their substance, 

 having distinctive chemical and odoriferous properties. 

 The preceding oils have carbon, hrdro^eu, and oxygen 

 solely as their constituents. The oils obtained from mus- 

 tard seed, onion, garlic, eschalots, horse-radish, and 

 assafoetida, contain also sulphur and nitrogen. The pre- 

 sence of sulphur in mustard is readily noticed by its well- 

 known action on the silver of mustard-spoons. These 

 articles of domestic use should, therefore, be gilt, so as 

 to prevent the production of the black sulphide of silver, 

 which so frequently covers the unprotected silver surface. 

 Mustard also affords a fixed oil, to winch allusion has 

 already been made. 



I! f -INS. Under this head some very interesting pro- 

 ducts range. They are generally obtained from the tree 

 affording them, by the process of "tapping," and the 

 juice which exudes soon acquires solidity. Ordinary 

 resin is thus a product of the pine, fir, larch, <fcc. 



Caoutchouc, or India-rubber, is one of the most valu- 

 able of these products. It is obtained by making a hole 

 in the stem of the Ficus Elastica. A milky juice passes 

 out, which gradually becomes solid. The natural colour 

 of caoutchouc is nearly white ; its dark tint is acquired 

 by the bottles into which it is made being smoked over 

 a fire. Caoutchouc is soluble in ether, some kinds of 

 naptha, and petroleum ; and, in this state, is used as a 

 varnish for waterproofing purposes. It is composed of 

 carbon and hydrogen, and is highly elastic and inflam- 

 mable. Mixed or worked up with sulphur, it loses a 

 portion of elasticity, but acquires other useful properties. 

 Its varied applications are well known ; and, with the 

 exception of gutta-percha, few vegetable products have 

 been so extensively employed in making articles of com- 

 fort and luxury. 



Gutta-percha is also the product of a tree, but differs 

 from India-rubber in many important respects. It is 

 less elastic, but does not lose its elasticity by being 

 heated to a high temperature, as is the case witli India- 

 rubber. In their chemical characteristics they also differ, 

 and in their solubility in menstrua. Both are non-con- 

 ductors of electricity, and have therefore been exten- 

 sively used for insulating telegraph wires. Electrical 

 machines have been made of each of these materials, and 

 they present great advantages to the electrician, owing to 

 the very slight deposition of moisture on their surface in 

 damp weather. The non-conducting power of heat pos- 



