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Encyclopedia Britannica - Main :: ANC-APO |
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ANIMAL . FA T S Name of Fat. Source. Yield per cent. Iodine Value. Principal Use. Drying Fats. Ice bear Ursus maritimus 147 Pharmacy Rattlesnake Crotalus durissus 106 Pharmacy Semi-drying Fats. Horses' fat. . ~ Equus cabatlus 75-85 Food, soap Non-drying Fats. Goose fat . Anser cinereus . 70 Food, pomades Lard Sus scrofa 50-70 Food, soap, candles Beef marrow Bos taurus 55 Pomades Bone . . Bos, Ovis . 46-56 Soap, candles Tallow, beef . Bos taurus 38-46 Food, soap, candles, lubricants Tallow, mutton Ovis aries 35-46 Food, soap, candles, lubricants Butter . Bos taurus 26-38 Food in hair or woollen bags and submitted to hydraulic pressure, by which a further portion of oil or fat is obtained (cf. Pressing, below). In the case of those animal fats which are intended for edible purposes, such as lard, suet for margarine, the greatest cleanliness must, of course, be observed, and the temperature must be kept as low as possible in order to obtain a perfectly sweet and pure material. Pressing.The boiling out process cannot be applied to small seeds, such as linseed and rape seed. Whilst the original method of obtaining seed oils may perhaps have been the same which is still used in India, viz. trituration of (rape) seeds in a mortar so that the oil can exude, it may be safely assumed that the process of expressing has been applied in the first instance to the preparation of olive oil.. The first woman who expressed olives packed in a sack by heaping stones on them may be considered as the forerunner of the inventors of all the presses that subsequently came into use. Pliny describes in detail the apparatus and processes for obtaining olive oil in vogue among his Roman contemporaries, who used already a simple screw press, a knowledge of which they had derived from the Greeks. In the East, where vegetable oils form an important article of food and serve also for other domestic purposes, various ingenious applications of lever presses and wedge presses, and even of combined lever and wedge presses, have been used from the remotest time. At an early stage of history the Chinese employed the same series of operations which are followed in the most advanced oil mills of modern time, viz. bruising and reducing the seeds to meal under an edge-stone, heating the meal in an open pan, and pressing out the oil in a wedge press in which the wedges were driven home by hammers. This primitive process is still being carried out in Manchuria, in the production of soja bean cake and soja bean oil, one of the staple industries of that country. The olive press, which was also used in the vineyards for expressing the grape juice, found its way from the south of France to the north, and was employed there for expressing poppy seed and rape seed. The apparatus was then gradually improved, and thus were evolved the modern forms of the screw press, next the Dutch or stamper press, and finally the hydraulic press. With the screw press, even in its most improved form, the amount of pressure practically obtainable is limited from the failure of its parts under the severe inelastic strain. Hence this kind of press finds only limited application, as in the industry of olive oil for expressing the best and finest virgin oil, and in the production of animal fats for edible purposes, such as lard and oleomargarine. The Dutch or stamper press, invented in Holland in the 17th century, was up to the early years of the 19th century' almost exclusively employed in Europe for pressing oil-seeds. It consists of two principal parts, an oblong rectangular box with an arrangement of plates,. blocks and wedges, and over it a framework with heavy stampers which produce the pressure by their fall. The press box first consisted of strongly bound oaken planks, but later on cast-iron boxes were introduced. At each extremity of the box a bag of oil-meal was placed between two perforated Iron plates, next to which were inserted filling-up pieces of wood, two of which were oblique, so that the wedges which exercised the pressure could be readily driven home. This press has had to yield place to the hydraulic press, although in some old-fashioned establishments in Holland the stamper press could still be seen at work in the 'eighties of the 19th century. The invention of the hydraulic press in 1795 by Joseph Bramah (Eng. pat., 3oth April 1795) effected the greatest revolution in the oil industry, bringing a new, easily controlled and almost unlimited source of power into play; the limit of the power being solely reached by the limit of the strength of the material which the engineer is able to produce. Since then the hydraulic press has practically completely superseded all other appliances-used for expression, and in consequence of this epoch-making invention, assisted as it was later on by the accumulatorinvented by William George (later Lord) Armstrong in 1843the seed-crushing industry reached a perfection of mechanical detail which soon secured its supremacy for England. The sequence of operations in treating oil seeds, oil nuts, &c., for the separation of their contained oils is at the present time as follows: As a preliminary operation the oil seeds and nuts are freed from dust, sand and other impurities by sifting in an inclined revolving cylinder or sieving machine, covered with woven wire;. having meshes varying according to the size and nature of the seed operated upon. This preliminary purification is of the greatest importance, especially for the preparation of edible oils and fats. In the case of those seeds amongst which are found pieces of iron ( hammer
on to the last, when the grains are sufficiently bruised, crushed and ground. The distance between the rollers can be easily regulated so that the seed leaving the bottom roller has the desired fineness. The comminuted mass, forming a more or less coarse meal, is either expressed in this state or subjected to a preliminary heating, according to the quality of the product to be manufactured. For the preparation of edible oils and fats the meal is expressed in the cold, after having been packed into bags and placed in hydraulic presses under a pressure of three hundred atmospheres or even more. The cakes are allowed to remain under pressure for about seven minutes. The oil exuding in the cold dissolves the smallest amount of colouring matter, &c., and hence has suffered least in its quality. Oils so obtained are known in commerce as " cold drawn oils," " cold pressed oils," " salad oils," " virgin oils." By pressing in the cold, obviously only part of the oil or fat is recovered. A further quantity is obtained by expressing the seed meal at a somewhat elevated temperature, reached by warming the comminuted seeds or fruits either immediately after they leave the five-roller mill, or after the " cold drawn oil " has been taken off. Of course the cold pressed cakes must be first disintegrated, which may be done under an edge-runner. The same operation may be repeated once more. Thus oils of the " second expression " and of the " third expression " are obtained. In the case of oleaginous seeds of low value (cotton-seed, linseed) it is of importance to express in one operation the largest possible quantity of oil. Hence the bruised seed is, after leaving the five-roller mill, generally warmed at once in a steam-jacketed kettle fitted with a mixing gear, by passing steam into the jacket, and sending at the same time some steam through a rose, fixed inside the kettle, into the mass while it is being agitated. This practice is a survival of the older method of moistening the seed with a little water, while the seeds were bruised under edge-runners, so as to lower the temperature and facilitate the bursting of the cells. The warm meal is then delivered through measuring boxes into closed pressbags (" scourtins " of the " Marseilles " press), or through measuring boxes, combined with an automatic moulding machine, into cloths open at two sides (Anglo-American press), so that the preliminarily pressed cakes can be put at once into the hydraulic press. In the latest constructions of' cage presses, the use of bags is entirely dispensed with, a measured-out quantity of seed falling direct into the circular press cage and being separated from the material forming the next cake by a circular plate of sheet iron. The essentials of proper oil pressing are a slowly accumulating pressure, so that the liberated oil may have time to flow out and escape, a pressure that increases in proportion as the resistance of the material increases, and that maintains itself as the volume of material decreases through the escape of oil. Numerous forms of hydraulic presses have been devised. Horizontal presses have practically ceased to be used in this branch of industry. At present vertical presses are almost exclusively in vogue; the three chief types of these have been already mentioned. Continuously working presses (compression by a conical screw) have been patented, but hitherto they have not been found practicable. Of the vertical presses the Anglo-American type of press is most in use. It represents an open press fitted with a number (usually sixteen) of iron press plates, between which the cakes are inserted by hand. A hydraulic ram then forces the table carrying the cakes against a press-head, and the exuding oil flows down the sides into a tank below. The " Marseilles press" is largely used in the south of France. There the meal is packed by hand in " scourtins," bags made of plaited coco-nut leavesreplacing the woollen cloths used in England. The packing of the press requires more manual
In the case of those seeds which contain more than 4o% of oil, such as arachis nuts and sesame seed, the first expression in pressbags leads to difficulty, as the meal causes " spueing," i.e. the meal exudes and escapes from the press. Hence, in modern installations, the first expression of those seeds is carried out in so-called cage (clodding) presses, consisting of hydraulic presses provided with circular boxes or cages, into which the meal is filled. These cages or boxes are either constructed of metal staves held together by a number of steel rings, or consist of one cylinder having a large number of perforations. The presses having perforated cylinders, although presenting mechanically a more perfect arrangement, are not preferable to the press cages formed by staves, as the holes become easily clogged up by the meal, when the cylinder must be carefully cleaned out. Modern improvements, with a view to cheapening of cost, effect the transport of the cages from one press battery to another on rails. In order to dispense even with the charging of the presses by hand, in some systems the cages are first charged in a preliminary press,from which they are transferred mechanically by a swinging arrangement into the final press. Whilst the meal is under pressure the oil works its way to the edge of the cake, whence it exudes. For this reason an oblong form is the most favourable one for the easy separation of the oil. The edges of the cakes invariably retain a considerable portion of oil; hence the soft edges are pared off, in the case of the oblong cake in a cake-paring machine, and the parings are returned to edge-runners, to be ground up and again pressed with fresh meal. Through the introduction of the cage (clodding) presses circular cakes have become fashionable, and as the material of these presses can be made much stronger and therefore higher pressure can be employed, more oil is expressed from the meal than in open presses. The oil flowing from the presses is caught in reservoirs placed under the level of the floor, from which it is pumped into storage tanks for settling and clarifying. Extraction by Solvents.The cakes obtained in the foregoing process still retain considerable proportions of oil, not less than 4 to 5 %usually, however, about to %. If it be desired to obtain larger quantities than are yielded by the above-described methods, processes having for their object the extraction of the seeds by volatile solvents must be resorted to. Extraction by means or carbon bisulphide was first introduced in 1843 by Jesse Fisher of Birmingham. Thirteen years later E. Deiss of Brunswick again patented the extraction by means of carbon bisulphide (Eng. Pat. No. 390, 1856), and added " chloroform, ether, essences, or benzine or benzole" to the list
The apparatus employed on a large scale depends on the temperature at which the extraction is carried out. In the main two types of extracting apparatus are differentiated, viz. for extraction in the cold and for extraction in the hot. The seed is prepared in a similar manner as for pressing, except that it is not reduced to a fine meal, so as not to impede the percolation of the solvent through the mass. In the case of cold extraction the seed is placed in a series of closed vessels, through which the solvent percolates by displacement, on the " counter-current " system. A battery of vessels is so arranged that one vessel can always be made the last of the series to discharge finished meal and to be recharged with fresh meal, so that the process is practically a continuous one. The solution of the extracted oil or fat is then transferred to a steam-heated still, where the solvent is driven off and recovered by condensing the vapours in a cooling coil, to be used again. The last remnant of volatile solvent in the oil is driven off by a current of open steam blown through the oil in the warm state. The extracting process in the hot is carried out in apparatus, the principle of which is exemplified by the well-known Soxhlet extractor. The comminuted seed is placed inside a vessel connected with an upright refrigerator on trays or baskets, and is surrounded there by the volatile solvent. On heating the solvent with steam through a coil or jacket, the vapours rise through and around the meal. They pass into the refrigerator, where they are condensed and fall back as a condensed liquid through the meal, percolating it as they pass downwards, and reaching to the bottom of the vessel as a more or less saturated solution of oil in the solvent. The solvent is again evaporated, leaving the oil at the bottom of the vessel until the extraction is deemed finished. The solution of fat is then run off into a still, as described already, and the last traces of solvent are driven out. The solvent is recovered and used again. With regard to the merits and demerits of the last two mentioned processes--expression and extractionthe adoption of either will largely depend on local conditions and the objects for which the pro-ducts are intended. Wherever the cake is the main product, expression will commend itself as the most advantageous process. Where, however, the fatty material forms the main product, as in the case of palm kernel oil, or sesame and coco-nut oils from damaged seeds (which would no longer yieid proper cattle food), the process of extraction will be preferred, especially when the price of oils is high. In some cases the combination of the two processes commends itself, as in the case of the production of olive oil. The fruits are expressed, and after the edible qualities and best class of oils for technical purposes have been taken off by expression, the remaining pulp is extracted by means of solvents. This process is known under the name of mixed process (huilerie mixte). Refining and Bleaching. The oils and fats prepared by any of the methods detailed above are in their fresh state, and, if got from perfectly fresh (" sweet ") material, practically neutral. If care be exercised in the process of rendering animal oils and fats or expressing oils in the cold, the products are, as a rule, sufficiently pure to be delivered to the consumer, after a preliminary settling has allowed any mucilaginous matter, such as animal or vegetable fibres or other impurities, and also traces of moisture, to separate out. This spontaneous clarification was at one time the only method in vogue. This process is now shortened by filtering oils through filter presses, or otherwise brightening them, e.g. by blowing with air. In many cases these methods still suffice for the production of commercial oils and fats. In special cases, such as the preparation of edible oils and fats, a further improvement in colour and greater purity is obtained by filtering the oils over charcoal, or over natural absorbent earths, such as fuller's earth. Where this process does not suffice, as in the case of coco-nut oil or palm kernel oil, a preliminary purification in a current of steam must be resorted to before the final purification, described above, is carried out. Oils intended for use on the table which deposit " stearine " in winter must be freed from such solid fats. This is done by allowing the oil to cool down to a low temperature and pressing it through cloths in a press, when a limpid oil exudes, which remains proof against cold" winter oil." Most olive oils are naturally non-congealing oils, whereas the Tunisian and Algerian olive oils deposit so much " stearine " that they must be " demargarina.ted." Similar methods are employed in the production of lard oil, edible cotton-seed oil, &c. For refining oils and fats intended for edible purposes only the foregoing methods, which may be summarized by the name of physical methods, can be used; the only chemicals permissible are alkalis or alkaline earths to remove free fatty acids present. Treatment with other chemicals renders the oils and fats unfit for consumption. Therefore all bleaching and refining processes involving other means than those enumerated can only be used for technical oils and fats, such .as lubricating oils, burning oils, paint oils, soap-making oils, &c. Bleaching by the aid of chemicals requires great circumspection. There is no universal method of oil-refining applicable to any and every oil or fat. Not only must each kind of oil or fat be considered as a special problem, but frequently even varieties of one and the same oil or fat are apt to cause the same difficulties as would a new individual. In many cases the purification by means of sulphuric acid, invented and patentedby Charles Gower in 1792 (frequently ascribed to Thenard), is still usefully applied. It consists in treating the oil with a small percentage of a more or less concentrated sulphuric acid, according to the nature of the oil or fat. The acid not only takes up water, but it acts on the suspended impurities, carbonizing them to some extent, and thus causing them to coagulate and fall down in the form of a flocculent mass, which carries with it mechanically other impurities which have not been acted upon. This method is chiefly used in the refining of linseed and rape oils. Purification by means of strong caustic soda was first recommended as a general process by Louis C. Arthur Barreswil, his suggestion being to heat the oil and add 2% to 3% of caustic soda. In most cases the purification consisted in removing the free fatty acids from rancid oils and fats, the caustic soda forming a soap with the fatty acids, which would either rise as a scum and lift up with it impurities, or fall to the bottom and carry down impurities. This process is a useful one in the case of cotton-seed oil. As a rule, however, it is a very precarious
risk
Oil Testing.Reliable scientific methods for testing oils and fats date back only to the end of the 'seventies of the 19th century. Before that time it was believed that not only could individual oils and fats be distinguished from each other by colour reactions, but it was also maintained that falsification could be detected thereby. With one or two exceptions (detection of sesame oil and perhaps also of cotton-seed oil) all colour reactions are entirely useless. The modern methods of oil testing rest chiefly on so-called " quantitative " reactions, a number of characteristic " values " being determined which, being based on the special nature of the fatty acids contained in each individual oil or fat, assist in identifying them and also in revealing adulteration. These " values," together with other useful methods, are enumerated in the order of their utility for the purposes of testing. The saponification value (saponification number) denotes the number of milligrams which one gramme of an oil or fat requires for saponification, or, in other words, for the neutralization of the total fatty acids contained in an oil or fat. We thus measure the alkali absorption value of all fatty acids contained in an oil or fat. The saponification values of most oils and fats lie in the neighbourhood of 195. But the oils belonging to the rape oil group are characterized by considerably lower saponification values, viz. about 175 on account of their containing notable quantities of erucic acid, CnH.t,O2. In the case of those oils which do not belong to the rape oils and yet show abnormally low saponification values, the suspicion is raised at once that a certain amount of mineral oils (which do not absorb alkali and are therefore termed " unsaponifiable ") has been admixed fraudulently. Their amount can be determined in a direct manner by exhausting the saponified mass, after dilution with water, with ether, evaporating the latter and weighing the amount of mineral oil left behind. A few of the blubber oils, like dolphin jaw and porpoise jaw oils (used for lubricating typewriting machines), have exceedingly high saponification values owing to their containing volatile fatty acids with a small number of carbon atoms. Notable also are coco-nut and palm-nut oils, the saponification numbers of which vary from 240 to 260, and especially butter-fat, which has a saponification value of about 227. These high saponification values are due to the presence of (glycerides of) volatile fatty acids, and are of extreme usefulness to the analyst, especially in testing butter-fat for added margarine and other fats. These volatile acids are specially measured by the Reichert value (Reichert-Wollny value). To ascertain this value the volatile acids contained in 5 grammes of an oil or fat are distilled in a minutely prescribed manner, and the distilled-off acids are measured by titration with decinormal alkali. Whereas most of the oils and fats, viz. all those the saponification value of which lies at or below 195, contain practically no volatile acids,i.e. have extremely low Reichert-Wollny values, all those oils and fats haying saponification'values above 195 contain notable amounts of volatile fatty acids. Thus, the Reichert-Meissl value of butter-fat is 25-30, that of coco-nut oil 6-7, and of palm kernel oil about 5-6. This value is indispensable for judging the purity of a butter. One of the most important values in oil testing is the iodine value. This indicates the percentage of iodine absorbed by an oil or fat when the latter is dissolved in chloroform or carbon tetrachloride, and treated with an accurately measured amount of free iodine supplied in the form of iodine chloride. By this means a measure is obtained of the unsaturated fatty acids contained in an oil or fat. On this value a scientific classification of all oils and fats can be based, as is shown by the above-given list
If one individual oil or fat is given, the iodine value alone furnishes the readiest means of finding its place in the above system, and in many cases of identifying it. Even if a mixture of several oils . and, fats be present, the iodine value assists greatly in the identification of the components of the mixture, and furnishes the most important key for the attacking and resolving of this not very simple problem. Thus it points the way to the application of a further method to resolve the isolated fatty acids of an oil or fat into saturated fatty acids, which do not absorb iodine, and into unsaturated fatty acids, which absorb iodine in various proportions as shown above. This separation is effected by converting the alkali soaps of the fatty acids into lead soaps and treating the latter with ether, in which the lead salts of the saturated acids are insoluble, whereas the salts of the above-named unsaturated acids are soluble. The saturated fatty acids can then be further examined, and valuable information is gained by the determination of the melting-points and by treatment with solvents. Thus some individual fatty acids, such as stearic acid and arachidic acid (which is characteristic of ground nut oil) can be identified. In the mixture of unsaturated fatty acids, by means of some more refined methods, clupanodonic acid, linolenic acid, linolic acid and oleic acid can be recognized. By combining the various methods which have been outlined here, and by the help of some further additional special methods, and by reasoning in a strictly logical manner, it is possible tc resolve a mixture of two oils and fats, and even of three and four, into their components and determine approximately their quantities. The methods sketched here do not yet exhaust the armoury of the analytical chemist, but it can only be pointed out in passing that the detection of hydroxylated acids enables the analyst to ascertain the presence of castor oil, just as the isolation and determination of oxidized fatty acids enables him to differentiate blown oils from other oils. Tests such as the Maumene test, the elaldin test and others, which formerly were the only resource of the chemist, have been practically superseded by the foregoing methods. The viscosity test, although of considerable importance in the examination of lubricating oils, has been shown to have very little discriminative value as a general test. Commerce.It may be safely said of the United Kingdom that it takes the foremost position in the world as regards the extent of the oil and fat industries. An estimate made by the writer (Cantor Lectures, " Oils and Fats, their Uses and Applications," Society of Arts, 1go4, p. 795), and based on the most. reliable information obtainable, led to the conclusion that the sums involved in the oil and fat trade exceeded 1,000,000 perweek; in 1907 they approximated 1,25o,000 per week. The great centres of the seed-oil trade (linseed, cotton-seed, rape-seed, castor-seed) are Hull, London, Liverpool, Bristol, Leith and Glasgow. Linseed is imported principally from the East Indies, Argentina, Canada, Russia and the United States; cotton-seed is chiefly supplied by Egypt and East India; rape-seed and castor-seed chiefly by East India. The importation of copra and palm kernels for the production of coco-nut oil and palm-nut oil is also considerable, but in these two cases Great Britain does not take the first place. Fish and blubber oils are principally produced in Dundee, London and Greenock. The manufacture of cod-liver oil for pharmaceutical purposes is naturally some-what limited, as Norway, Newfoundland, and latterly also Japan, are more favourably situated as regards the supply of fresh cod, but the technical liver oils (cod oil, shark-liver oil) are produced in very large quantities in Grimsby, Hull, Aberdeen, and latterly also on the west coasts of the United Kingdom. The production of edible fats (margarine, lard compounds, and vegetable butters) has taken root in this country, and bids fair to extend largely. With regard to edible oils, edible cotton-seed oil is the' only table oil produced in Great Britain. The United Kingdom is also one of the largest importers of fatty materials. Practically the whole trade in palm oil, which comes exclusively from West Africa, is confined to Liverpool, and the bulk of the tallow imported into Europe from Australasia, South America and the United States, is sold in the marts of London and Liverpool. Lard reaches Great Britain chiefly from the United States. Amongst the edible oils and fats which are largely imported, butter takes the first rank (to an amount of almost 25,000,000 per annum). This food-stuff reaches Great Britain not only from all butter-exporting countries of the continent of Europe, but in increasing quantities also from Australia, Canada, Argentine, Siberia and the United States of America. Next in importance is margarine, the British production of which does not suffice for the consumption, so that large quantities must be imported from Holland, edible olive oil from Italy, the south of France, Spain and the Mediterranean ports generally. Coco-nut oil and copra, both for edible and technical purposes, are largely shipped to Great Britain from the East Indies and Ceylon, Java and the West Indies. Of lesser importance are greases, which form the by-product of the large slaughter-houses in the United States and Argentina, and American (Canadian) and Japanese fish oils. On the continent of Europe the largest oil-trading centres are on the Mediterranean (Marseilles and Triest), which are geographically more favourably placed than England for the production of such edible oils (in addition to the home-grown olive oil) as arachis oil, sesame oil and coco-nut oil. Moreover, the native population itself constitutes a large consumer of these oils. In the north of Europe, Hamburg, Rotterdam, Antwerp and Copenhagen are the largest centres of the oil and fat trade. Hamburg and its neighbourhood produces, curiously enough, at present the largest amount of palm-nut oil. The United States takes the foremost place in the world for the production of cotton-seed and maize oils, lard, bone fat and fish oils. Canada is likely to outstrip the United States in the trade of fish and blubber oils, and in the near future Japan bids fair to become a very serious competitor in the supply of these oils. Vast stores of hard vegetable fats are still practically wasted in tropical countries, such as India, Indo-China and the Sunda Islands, tropical South America, Africa and China. With the improvement in transport these will no doubt reach European manufacturing centres in larger quantities than has been the case hitherto. WAXES The waxes consist chiefly of the fatty acid esters of the higher monohydric alcohols, with which are frequently associated free alcohols as also free fatty acids. In the following two tables the " acids " and " alcohols " hitherto identified in waxes are .enumerated in a classified order: AcIns Boiling Point. Melting Point. I C. Characteristic of Pmm.ressure. C I. Acids of the Acetic series CH2n02 C13H2602 .. .. 57 Gondang wax Ficocerylic acid . Myristic acid . . C14H2802 IOC. 250`5 53'8 Wool wax Palmitic acid . . C16H32Q2 too 271'5 62.62 Beeswax, spermaceti Carnaiibic acid . C24H4802 .. 72.5 Carnauba wax, wool wax Pisangcerylic acid . . . C24H4802 . .. 71 Pisang wax Cerotic acid . C26H52O2 .. 77.8 Beeswax, wool wax, insect wax lVielissic acid . . C36H6602 .. .. 91 Beeswax Psyllostearylic acid . C36H6602 . . . 9495 Psylla wax II. Acids of the Acrylic or Oleic series CnH2, ..2 02 Physetoleic acid . C16H36O2 .. 30 Sperm oil Doeglic acid (?) C19H2602 .. . . Lanopalmic acid . Cocceric acid . . C31H6203 92-93 Cochineal wax I V. Dihydroxylated acids of the series CH2n04 C26H6604 .. .. 104105 Wool wax Lanoceric acid ALCOHOLS Boiling Point. Melting point. mm C C. Characteristic of Pressure. L Alcohols of the Ethane series CHzn+20 C16H340 . .. 78 Pisang wax Pisangceryl alcohol Cetyl alcohol (Ethal) . C16H160 76o 344 5o Spermaceti Octodecyl alcohol . C,8H380 15 210'5 59 Carnaubyl alcohol . C241-150O .. .. 68-69 Wool wax Ceryl alcohol . C26H64O .. .. 79 Chinese wax, opium wax, wool fat Myricyl (Melissyl) alcohol . C36H62O .. .. 85-88 Beeswax, Carnauba wax Psyllostearyl alcohol C22H68O .. .. 687o Psylla wax II. Alcohols of the Allylic series CH2n0 C12H240 .. .. ' 102104 Wool wax Lanolin alcohol . . . Ficoceryl alcohol . . . IV. Alcohols of the Glycolic series CnH2n+202 C36H62O2 .. .. 101-104 Cochineal wax Cocceryl alcohol . . . . V. Alcohols of the Cholesterol series C26H440 .. 148'4-150.8 Wool wax Cholesterol . . Isocholesterol . C26H440 .. .. 137-138 Spermaceti consists practically of cetyl palmitate, Chinese wax of ceryl palmitate. The other waxes are of more complex composition, especially so wool wax. The waxes can be classified similarly to the oils and fats as follows: I. Liquid waxes. II. Solid waxes. A. Vegetable waxes. B. Animal waxes. The table enumerates the most important waxes:WAXES There are only two liquid waxes known, sperm oil and arctic sperm oil (bottlenose-whale oil), formerly always classed together with the animal oils. In their physical properties the natural waxes simulate the fatty oils and fats. They behave similarlyto solvents; and in their liquid condition leave a grease spot on paper. An important property of waxes is that of easily forming emulsions with water, so that large quantities of water can be incorporated with them (lanolin). The liquid waxes occur in the blubber of the sperm whale, and in the head cavities of those whales which yield spermaceti; this latter is obtained by cooling the crude oil obtained from the head cavities. Vegetable waxes appear to be very widely distributed throughout the vegetable kingdom, and occur mostly as a very thin film covering leaves and also fruits. A few only are found in sufficiently large quantities to be of com- mercial importance. So far carnaiiba wax is practically the only vegetable wax which is of importance in the world's markets.. The animal waxes are widely distributed amongst the insects, the most important being beeswax, which is collected in almost all parts of the world. An ex- ceptional position is occupied by wool wax, the main constituent of the natural wool fat which covers the hair of sheep, and is obtained as a by-product in scour- ing the raw wool. Wool fat is now being purified on a large scale and brought into commerce, under the name of lanolin, as an Name of Wax. Source. Iodine Principal Use. Value. Liquid Waxes. Sperm oil. Physeter macrocephalus . 81-90 Lubricant Arctic sperm oil (Bottlenose oil) Hyperoodon rostratus 6782 Lubricant Vegetable Waxes Solid Waxes. 13 Polishes. Phonograph mass Carnauba wax . .. Corypha cerifera . Animal Waxes Ovis aries 102 Ointment Wool wax . . Beeswax Apis mellifica . 8.11 Candles, polishes Spermaceti (Cetin) Physeter macrocephalus 04 Candles, surgery Insect wax, Chinese wax . Coccus ceriferus . I 01.4 Candles, polishes, sizes ointment the beneficent properties of which were known to Dioscorides in the beginning of the present era. Its chemical composition is exceedingly complex, and specially remarkable on account of the considerable proportions of cholesterol and isocholesterol it contains. Commerce.The sperm oils are generally sold in the same markets as the fish and blubber oils (see above). For beeswax London is one of the chief marts of the world. In Yorkshire, the centre of the woollen industry, the largest amounts of wool-fat are produced, all attempts to recover the hitherto wasted material in Argentine and Australia having so far not been attended with any marked success. Spermaceti is a comparatively unimportant article of commerce; and of Chinese wax . small quantities only are imported, as the home consumption takes up the bulk of the wax for the manufacture of candles, polishes and sizes. 2. Essential or Ethereal Oils. The essential, ethereal, or " volatile " oils constitute a very extensive class of bodies, which possess, in a concentrated form, the odour characteristic of the plants or vegetable substances from which they are obtained. The oils are usually contained in special cells, glands, cavities, or canals within the plants either as such or intermixed with resinous substances; in the latter case the mixtures form oleo-resins, balsams or resins according as the product is viscid, or solid and hard. A few do not exist ready formed in the plants, but result from chemical change of inodorous substances; as for instance, bitter almonds and essential oil of mustard. The essential oils are for the most part insoluble or only very sparingly soluble in water, but in alcohol, ether, fatty oils and mineral oils they dissolve freely. They ignite with great ease, emitting a smoke freely, owing to the large proportion of carbon they contain. Their chief physical distinction from the fatty oils is that they are as a rule not oleaginous to the touch and leave no permanent grease spot. They have an aromatic smell and a hot burning taste, and can be distilled unchanged. The crude oils are at the ordinary temperature mostly liquid, some are solid substances, others, again, deposit on standing a crystalline portion (" stearoptene " in contradistinction to the liquid portion (" elaeoptene "). The essential oils possess a high refractive power, and most of them rotate the plane of the polarized light. Even so nearly related oils as the oils of turpentine, if obtained from different sources, rotate the plane of the polarized light in opposite directions. In specific gravity the essential oils range from 0.850 to 1.142; the majority are, however, specifically lighter than water. In their chemical constitution the essential oils present no relationship to the fats and oils. They represent a large number of classes of substances of which the most important are: (t) Hydrocarbons, such as pinene in oil of turpentine, camphene in citronella oil, limonene in lemon and orange-peel oils, caryophyllene in clove oil and cumene in oil of thyme; (2) ketones, such as camphor from the camphor tree, and irone which occurs in orris root; (3) phenols, such as eugenol in clove oil, thymol in thyme oil, saffrol in sassafras oil, anethol in anise oil; (q.) aldehydes, such as citral and citronellal, the most important constituents of lemon oil and lemon-grass oil, benzaldehyde in the oil of bitter almonds, cinnamic aldehyde in cassia oil, vanillin in gum benzoin and heliotropin in the spiraea oil, &c.; (5) alcohols and their esters, such as geraniol (rhodinol) in rose oil and geranium oil, linalool, occurring in bergamot and lavender oils, and as the acetic ester in rose oil, terpineol in cardamom oil, menthol in peppermint oil, eucalyptol in eucalyptus oil and borneol in rosemary
Preparation from Plants.Before essential oils could be prepared synthetically they were obtained from plants by one of the following , methods : (r) distillation, (2) expression, (3) extraction, (4) enfleurage, (5) maceration. The most important of these processes is the first, as it is applicable to a large number of substances of the widest range, such as oil of peppermint,and camphor. The process is based on the principle that whilst the odoriferous substances are insoluble in water, their vapour tension is reduced on being treated with steam so that they are carried over by a current of steam. The distillation is generally performed in a still with an inlet for steam and an outlet to carry the vapours laden with essential oils into a condenser, where the water and oil vapours are condensed. On standing, the distillate separates into two layers, an aqueous and an oily layer, the oil floating on or sinking through the water according to its specificgravity. The process of expression is applicable to the obtaining of essential oils which are contained in the rind or skin of the fruits belonging to the citron family, such as orange and lemon oils. The oranges, lemons, &c., are peeled, and the peel is pressed against a large number of fine needles, the exuding oil being absorbed by sponges. It is intended to introduce machinery to replace manual
flowers
Synthetic Preparation.Since the chemistry of the essential oils has been investigated in a systematic fashion a large number of the chemical individuals mentioned above have been isolated from the oils and identified. This first step has led to the synthetical production of the most characteristic substances of essential oils in the laboratory, and the synthetical manufacture of essential oils bade fair to rival in importance the production of tar colours from the hydrocarbons obtained on distilling coal. One of the earliest triumphs of synthetical chemistry in this direction was the production of terpineol, the artificial lilac
A pplications.Essential oils have an extensive range of uses, of which the principal are their various applications in perfumery (q.v.). Next to that they play an important part in connexion with food. The value of flavouring herbs, condiments and spices is due in a large measure to the essential oils contained in them. The commercial value of tea, coffee, wine and other beverages may be said to depend largely on the delicate aroma which they owe to the presence of minute quantities of ethereal oils. Hence, essential oils are extensively used for the flavouring of liqueurs, aerated beverages and other drinks. Nor is their employment less considerable in the manufacture of confectionery and in the preparation of many dietetic articles. Most fruit essences now employed in confectionery are artificially prepared oils, especially is this the case with cheap confectionery (jams, marmalades, &c.) in which the artificial fruit esters to a large extent replace the natural fruity flavour. Thus amyl acetate is used as an imitation of the jargoneile-pear flavour; amyl valerate replaces apple flavour, and a mixture of ethyl and propyl butyrates yields the so-called pine-apple flavour. Formic ether gives a peach-like odour, and is used for flavouring fictitious rum. Many of the essential oils find extensive use in medicine. In the arts, oil of turpentine is used on the largest scale in the manufacture of varnishes, and in smaller quantities for the production of terpineol and of'artificial camphor. Oil of cloves is used in the silvering of mirror glasses. Oils of lavender and of spike are used as vehicles for painting, more especially for the painting of pottery and glass. The examination of essential oils is by no means an easy task. Each oil requires almost a spacial method, but with the progress of chemistry the extensive adulteration that used to be practised with fatty oils has almost disappeared, as the presence of fatty oils is readily detected. Adulteration of expensive oil with cheaper oils is now more extensively practised, and such tests as the determination of the saponification value (see above) and of the optical rotation, and in special cases the isolation and quantitative determination of characteristic substances, leads in very many cases to reliable results. The colour, the boiling-point, the specific gravity and solubility in alcohol serve as most valuable adjuncts in the examination with a view to form an estimate of the genuineness and value of a sample. Quite apart from the genuineness of a sample, its special aroma constitutes the value of an oil, and in this respect the judging of the value of a given oil may, apart from the purity, be more readily solved by an experienced perfumer than by the chemist. Thus roses of different origin or even of different years will yield rose oils of widely different value. The cultivation of plants for essential oils has become a large industry, and is especially practised as an industry in the south of France (Grasse, Nice, Cannes). The rose oil industry, which had been for centuries located in the valleys of Bulgaria, has now been taken up in Germany (near Leipzig
illustration
For the essential oils, see F. B. Power, Descriptive Catalogue of Essential Oils; J. C. Sawer, Odorographia (London, 1892.and 1894); E. Gildemeister and F. Hoffmann, Die aetherischen Ole (Berlin, 1899), trans. (1900) by E. Kremers under the title Volatile Oils (Milwaukee, Wisconsin) ; F. W. Semmler, Die aetherischen Ole nach ihren chemischen Bestandteilen unter Beriicksichtigung der geschichtlichen Entwickelung ( Leipzig
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