SIR H. DAVY S AGRICULTURAL CHEMISTRY. 



133 



Sumatra, Borneo, and other of the 

 East India Isles. It has been obtained 

 from thyme {Thyi7ius serpillum,) mar- 

 jorum {Origanum viajorana,) gino;er 

 tree {Ammonium zingiber,) sage {Sulvis 

 officinalis.) Many volatile oils yield i 

 camphor by being merely exposed to the 

 air. An artificial substance very similar 

 to camphor has been formed by M. Kird, 

 by saturating oil of turpentine with 

 muriatic acid gas (the gaseous substance 

 procured from common salt by the action 

 of sulphuric acid.) The camphor pro- 

 cured in well conducted experiments 

 amounts to half of the oil of turpentine 

 used. It agrees with common camphor 

 in most of its sensible properties; but 

 differs materially in its chemical qualities 

 and composition. It it not soluble with- 

 out decomposition in nitric acid. From 

 the experiments of Gehlen, it appears to 

 consist of the elements of oil of turpentine, 

 carbon, hydrogen, and oxygen, united to 

 the elements of muriatic gas, chlorine, 

 and hydrogen. 



From the analogy of artificial to natural 

 camphor, it does not appear improbable 

 that natural camphor may be a secondary 

 vegetable compound, consisting of cam- 

 phoric acid and volatile oil. Camphor 

 is used medicinally, but it has no other 

 application. 



15. Fixed oil is obtained by expres- 

 sion from seeds and fruits ; the olive, the 

 almond, linseed, and rapeseed afford the 

 most common vegetable fixed oils. The 

 properties of fixed oils are well known. 

 Their specific gravity is less than that of 

 water; that of olive and of rapeseed 

 oil is 913; that of linseed and almond 

 oil 932; that of palm oil 968; that of 

 walnut and beechmast oil i)23. Many 

 of the fixed oils congeal at a lower 

 temperature than that at which water 

 freezes. They all require for their eva- 

 poration a higher temperature than that 

 at which water boils. The products of 

 the combustion of oil are water and car- 

 bonic acid gas. 



From the experiments of Gay Lussac 

 and Thenard, it appears that olive oil 

 contains, in 100 parts, 

 Carbon - - - - _ 77.213 



Oxygen 9.427 



Hydrogen . - . . 13.3G0 



This estimation is a near approxima- 

 tion to 11 proportions of carbon, 20 hy- 

 drogen, and 1 oxygen. 



The following is a list of fixed oils, and 

 of the trees that afford them. — Olive oil, 

 from tiie olive tree [Olea Europea;) lin- 

 seed oil, from the common and perennial 

 flax [Linum usilalissinmm et perenne;) 

 nut oil, from the hazelnut (Cori/lhis 

 avellana ;) walnut {Juglans regia ;) 

 hemp oil, from the hemp {Cannabis sa- 

 liva;) almond oil, from the sweet al- 

 mond {Jlmygdalus communis:) beech 

 oil, from the common beech {Fagus syl- 

 vatica;) rapeseed oil, from the rapes 

 {Brassica napiis et campestris;) poppy 

 oil, from the poppy {Papaver SQrnnife- 

 rum;) oil of sesamum, from the sesamum 

 {Sesamiim, orientale;) cucumber oil, 

 from the gourds {Cucurbit apepo et ma- 

 lapepo;) oil of mustard {Sinapis nigra 

 et arvensis;) oil of sunflower, from the 

 annual and perennial sunflower {Helian- 

 thus annuus et perennis;) castor oil, 

 from the palma christi {Ricinus commu- 

 nis;) tobacco {Nicotiana tabacum et 

 ruslica;) plum kernel oil, from the plum 

 tree {Prunus domestica; grapeseed oil, 

 from the vine ( Vitis vinifera:) butter of 

 cocoa, from the cocoa tree {Theobram.a 

 cacoa;) laurel oil, from the sweet bay 

 tree {Laurus nobilis.) 



The fixed oils are very nuti'itive sub- 

 stances; they are of great importance in 

 their applications to the purposes of life. 

 Fixed oil, in combination with soda, 

 forms the finest kind of hard soap. The 

 fixed oils are used extensively in the 

 mechanical arts, and for the preparation 

 of pigments and varnishes. 



16. Volatile o«7, likewise called essen- 

 tial oil, differs from fixed oil, in being 

 capable of evaporation by a much lower 

 degree of heat; in being soluble in al- 

 cohol, and in possessing a very slight 

 degree of solubility in water. 



There is a great number of volatile 

 oils, distinguished by their smell, their 

 taste, and their specific gravity, and other 

 sensible qualities. A strong and peculiar 

 odor may however be considered as the 

 great characteristic of each species; the 

 volatile oils inflame with more facility than 

 the fixed oils, and afford by their com bus- 



