97 



FISTULA LACKYMALIS. 



FIXED OILS. 



the 16th century, attempted to find a passage through the northern 

 ocean to India, that we owe the discovery which led to the establish- 

 ment of the fishery in the seas of Greenland and Spitzbergen. The 

 English and the Dutch were the first to embark in this adventure ; 

 1 nit the French, Danes, Hamburghers, and others were not slow to 

 follow their example. At first the whales were so numerous that the 

 fishing was comparatively easy, and was so successfully pursued that, 

 in addition to the ships actually engaged in the fishery, many other 

 vessels were sent in ballast to the shores of Spitzbergen, and the whole 

 returned home with full cargoes of oil and whalebone. It was then 

 the practice to boil the blubber on the spot, and bring home the oil in 

 casks. In the progress of the fishery the whales became less numerous, 

 and, when found, more difficult to take. It therefore became necessary 

 to pursue them farther to the open sea, and at length it was found 

 more economical to bring the blubber home in order to its being 

 boiled, and the settlements before used for that purpose were aban- 

 doned. That part of the Arctic Sea which lies between Spitzbergen 

 and Greenland, and which was formerly frequented by the whale ships, 

 is now almost wholly abandoned because of the scarcity of the fish, 

 and the northern whale fishery is now chiefly pursued in Davis's 

 Straits. Previous to the revolt of the North American provinces this 

 fishery, aa well as that in the Southern Ocean, was prosecuted with 

 great spirit by the colonists of Massachusetts. Just before the begin- 

 ning of the war they employed annually 183 ships of 13,820 tons in 

 the Northern, and 121 ships of 14,026 tons in the Southern whale 

 fisheries. 



It was not until after the breaking out of war between England 

 and the American provinces had, for a time at least, interrupted 

 [ilrit of enterprise, that England embarked in the Southern 

 fishery. Towards the close of the last century, the number of English 

 vessels so employed was considerable ; in 1791 they amounted to 75, but 

 the number has since greatly fluctuated. It requires a considerable sum 

 of money to fit out a ship. A new vessel of the size usually employed 

 350 tons coats, when ready for sea and fully provisioned, from 

 12,000?. to 15,000/. ; and the adventurer must wait three years for the 

 return of his capital. 



FISTULA LACRYMALIS. [LACBVMAL ORGAMS, DISEASES OP.] 



FIT. [SYNCOPE.] 



FIXED AIR. [CARBONIC ACID.] 



FIXED OILS. The fixed oils constitute an important division of 

 that well-known group of natural substances generically termed fatty 

 matters. The name oil sufficiently indicates the liquid character of 

 the members of this division ; and they are said to be fi.red, because 

 they may be heated to nearly 500* Fahr. without undergoing material 

 change, that degree of heat being far above the temperature necessary 

 for the perfect volatilisation of any of the essential oils another 

 division of the fatty group. [ESSENTIAL OILS.] 



Source. Fixed oils are mainly obtained from the vegetable kingdom, 

 reading for the most part in the seed, but occasionally in the fruit of 

 plants. Certain cold-blooded animala, notably the cod-fish, and several 

 cetaceans, such as the sperm whale, also furnish fixed oils of consider- 

 able economic value. [OILS, in NAT. HIST. Div.] 



Preparation. The most usual method of obtaining a fixed oil is by 

 submitting the substance from which it ig to be extracted to strong 

 pressure. For this purpose hydraulic presses are very generally 

 yed. Heat is occasionally made use of to increase the liquidity 

 of the oil, the plates of the press being kept hot for this purpose, and 

 the substance itself usually previously exposed in bags to the action of 

 steam. Oil obtained in this way may be rendered quite bright and 

 transparent, either by subsidence, or filtration through paper or flannel. 

 Another process for obtaining fixed oil consists simply in boiling the 

 substance with water, when the oil rises to the surface and may be 

 i-d off. A useful laboratory method of extraction is digestion 

 substance in alcohol or ether, or a mixture of the two, and sub- 

 sequent separation of the solvent by heat. 



'Jication. But few oils are at once obtained from their natural 

 source in a state fit for use, and no generally applicable process can bo 

 I by which they may be refined and bleached. Exposure to light 

 in glass bottles is sufficient to decolorise many of them. Digestion 

 with strong sulphuric acid for a time, and subsequent treatment either 

 with cold water, or if necessary with steam, or simply blowing steam 

 through the oil without the addition of sulphuric acid, are other 

 methods of purification. Tannic acid, under the form of a strong 

 decoction of oak bark, is occasionally employed to separate albuminous 

 and gelatinous matter. Caustic soda, in small quantity, with the aid of 

 heat, will generally separate sulphur contained in an oil, and improve 

 its appearance and odour. Chromic acid is perhaps the most energetic 

 oil-bleaching agent. It is conveniently applied by adding to the oil a 

 Maturated solution of bichromate of potash containing nearly half its 

 weight of strong sulphuric acid. The rancidity of oils may be removed 

 by washing with cold water alone, or with a very dilute aqueous 

 alkaline solution. 



Properties. The fixity of the bodies under consideration is obviously 

 their great characteristic. Their specific gravity is always less than 

 that of water, ranging from 0'90 to 0'93. Their consistence varies ; 

 heat renders them more liquid, cold congeals or solidifies them. When 

 perfectly pure they have little or no smell, but as usually met with 

 possess more or less characteristic odours, due to the presence of such 



ARTS AND SCI. DIV. VOL. IV. 



volatile matters as butyric, valeric, or caproie acid, &c. "\Vhen . these 

 matters are present in excess, oils are said to be rancid. 



The fixed oils are insoluble in water, and, with the exception of 

 castor oil, almost insoluble in alcohol ; they however readily dissolve 

 in ether, benzole, and oil of turpentine, and are miscible in all pro- 

 portions with each other and with the essential oils. When heated in 

 close vessels to 500 or 600 Fahr. they are decomposed, irritating 

 vapours are evolved, and permanently gaseous bodies, as well as some 

 liquid and solid substances, are produced. These products are all in- 

 flammable, burning with a luminous flame ; indeed an ordinary oil- 

 lamp is a miniature apparatus for the combustion of the products of 

 the destructive distillation of oil. [CAUDLE MANUFACTURE.] 



In chemical composition the fixed oils greatly resemble each other. 

 They contain FATTY ACIDS, in slightly variable proportions, united 

 with glycerin : the oleate of glycerin, however, preponderating. 

 Ammonia acts upon fixed oils, converting them into amides ; but the 

 other caustic alkalies, and some metallic oxides, form with them true 

 soaps. All fixed oils are more or less acted upon when exposed to the 

 air. Some slightly thicken and acquire rancidity, but do not become 

 solid ; others rapidly absorb oxygen, give out heat, and ultimately dry 

 up into a kind of resin. When the latter kind of oils are exposed to 

 the air in a finely divided state, such as occurs when paper, cotton, 

 shavings, straw, &c., are saturated with them, this oxidising action 

 goes on at such a rate that the heat evolved is sufficient to cause the 

 inflammation of the mass. [COMBUSTION, Spontaneous.] 



Drying and non-dryiwj oils. From what has just been stated, it is 

 evident that fixed oils may be divided into these two classes. The 

 principal dryiny oih are those of linseed, poppy, sperm, walnut, cod- 

 liver and hemp. They are largely used in the preparation of varnishes 

 and by the painter as vehicles for pigments. Their drying property is 

 considerably increased by heating them with litharge (oxide of lead) 

 or with oxide of manganese ; they are then technically termed boiled 

 oili. The chief non-drying oils are those of almond, colza, olive, rape, 

 as well as all that are of animal origin : they are further distinguished 

 from the drying oils by being converted into the solid state by 

 mercurous nitrate or by ^th part of their weight of peroxide of 

 nitrogen (NO,), and are used in cookery, for lubricating machinery, 

 and for burning in lamps. 



Tots fur purity. General tests for the purity of fixed oils are smell, 

 taste, and specific gravity. Special tests for the principal of them 

 will be found described under their respective names. The action of 

 sulphuric acid is also a valuable aid in individualising the fixed oils ; 

 a table of the action of, and details concerning, this reagent will be 

 found in ' Cooley's Cyclopaedia of Practical Receipts,' article ' Oils.' 



Another systematic method, by Calvert, is described in ' Muspratt's 

 Chemistry ' as applied to the arts and manufactures, article ' Oil.' 



Alphabetical list of the chief fixed oili. 



Almond oil. [AMYODALUS.] A non-drying oil. 



Appleseedoil. Obtained by expression from apple-pips. It resembles 

 poppy oil. 



Say oil. Non-drying. [LAURUS NOBILIS in NAT. HIST. Div.] 



Beech, oil. Non-drying. Sp. gr. 0'9225. [BEECH. FAQUS in NAT. 

 HIST. Div.] 



Belladonna, oil. From the fruit of Atropa Belladonna. Sp. gr. 

 0-925 : a drying oil. 



Ben oil. [BEN, OIL OF.] Non-drying. 



Cacao oil. [CACAO.] Non-drying. 



Camelina oil. From the seed. [CAMF.LINA SATIVA in NAT. HIST. 

 Div.] Drying. Sp. gr. 0'9252. 



Carapa oil. From the fruit. [CABAPA in NAT. HIST. Div.] 



Castor oil. Obtained by expression from the seeds of Sicinus 

 Communis. Sp. gr. 0'969. Dries by very long exposure. Its 

 nauseous taste is said to be removed by agitation with magnesia. Is 

 miscible with alcohol. Contains a modification of oleic acid termed 

 ncinoleic acid. Heated with caustic potash, sebacic acid is produced, 

 hydrogen is evolved, and caprylic alcohol distils over. 



Cebaditta oil. From the seed. [CEBADILLA in NAT. HIST. Div.] 



Cheriy-stone oil. From the kernel. Sp. gr. 0'9239. 



Chestnut oil. From horse-chestnuts. Non-drying. Sp. gr. 0'927. 



Cocoa-nut oil. Non-drying. Solid at common temperatures. 

 [Cocos, in NAT. HIST. Div.] 



Cod-liver oil. From the liver of the common cod-fish. [MORRHUA 

 vulgaris in NAT. HIST. Div.] To obtain a pure pale yellow oil for 

 medicinal purposes, the livers, after washing with cold water, are sub- 

 mitted to gentle heat in steam-jacket pans for about three quarters of 

 an hour; on cooling, the oil separates and floats on the surface, is 

 skimmed off and clarified by subsidence in deep cisterns and by filtra- 

 tion, first through flannel, and finally through moleskin under pressure. 

 It is exported from Newfoundland in casks, one manufacturer alone 

 producing between 20,000 and 30,000 gallons annually. 



Other cod-liver oils occur in commerce ; they are all of a more or 

 less brown colour, and are obtained from the livers after exposure to 

 the sun. The livers undergo putrefactive fermentation, and yield a 

 larger per centage of oil than when treated as already described for the 

 medicinal oil. The livers of other fish than the cod are also used in 

 the manufacture of common cod oil. It is principally used by curriers 

 for dressing leather. 



