# 1911 Encyclopædia Britannica/Paraffin

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​PARAFFIN, the name given to a mineral wax and oil, and also used as a generic name of a particular series of hydrocarbons.
Commercial Paraffin.—Refined commercial paraffin is a white or bluish-white, translucent, waxy solid substance, of lamino-crystalline structure, devoid of taste and smell, and characterized by chemical indifference. It consists of about 85% of carbon and 15% of hydrogen. Although the credit of having first (in 1830) investigated the properties of solid paraffin, obtained from wood-tar, belongs to Karl Reichenbach, the existence of paraffin in petroleum had been more or less hazily known for some time previous. In 1809 Fuchs found solid hydrocarbons in the Tegernsee oils, and in 1819 Buchner
separated them from these oils in comparative purity. By the latter they were described as “mountain-fats,” and they were identified with paraffin in 1835 by von Kobel. Reichenbach described the results of a series of experiments on the reactions between various substances and paraffin, and on account of the inert nature of the material gave to it its present name (from the Lat. parum, too little, and affinitas, affinity); he expressly stated that the accent should fall on the second “a,” but usage has transferred it to the first.
Paraffin was obtained by Laurent in 1830 by the distillation of bituminous schist, and in 1835 by Dumas from coal-tar; but the product appears to have been regarded only as a curiosity, and Lord Playfair has stated that prior to 1850 he never saw a piece of more than one ounce in weight. Paraffin is asserted to have been made for sale by Reichenbach’s process from wood-tar by John Thom, of Birkacre, before 1835. In 1833 Laurent suggested the working of the Autun shale, and products manufactured from this material were exhibited by Selligue in 1839.
According to F. H. Storer, the credit of having first placed the manufacture of paraffin on a commercial basis is deservedly given to Selligue, whose patent specifications, both in France and England, sufficiently clearly show that his processes of distilling bituminous schist, &c., and of purifying the distillate, had reached considerable perfection prior to 1845. In its present form, however, the paraffin or shale-oil industry owes its existence to Dr James Young. In 1850 he applied for his celebrated patent (No. 13,292) “for obtaining paraffine oil, or an oil containing paraffine, and paraffine from bituminous coals” by slow distillation. The process was extensively carried out in the United States under licence from Young, ​ until crude petroleum was produced in that country in such abundance, and at so low a cost, that the distillation of bituminous minerals became unprofitable. The highly bituminous Boghead coal, or Torbanehill mineral, which yielded 120 to 130 gallons of crude oil per ton, was worked out in 1862, and since then the Scottish mineral oils and paraffin have been obtained from the bituminous shales of the coal-measures, the amount of such shale raised in Great Britain in 1907 being 2,690,028 tons.
The following list represents an attempt to assign a geological age to the various occurrences of oil-shale and similar substances throughout the world:—
Oil-Shales :
| Geological System. | Locality. |
| Miocene | France (Vagnas), Servia. |
| Eocene | Brazil. |
| Cretaceous | Syria, Montana, New Zealand. |
| Neocomian | Spain. |
| Jurassic | Dorset, Württemberg. |
| Permian | France (Autun, &c.). |
| Carboniferous | Scotland, Yorkshire, Stafford,  Flint, France, Nova Scotia. |
| Kerosene-Shale ||
| Permo-Carboniferous | Queensland, New South Wales,  Tasmania. |
| Tar-Lignite ||
| Miocene | Moravia, Lower Austria, Bavaria.  Rhenish Prussia, Hesse, Saxony. |
| Oligocene | Bohemia, Tirol. |
Oil-Shale.—The oil-shale of Scotland is dark grey or black, and has a laminated or horny fracture. Its specific gravity is about 1·75, and 20 cub. ft. of it weigh rather less than a ton. The richer kinds yield about 30 gallons of oil per ton of shale, and in some cases as much as 40 gallons, but the higher yield is usually obtained at the expense of the solid paraffin and of the quality of the heavy oils. The inferior shales yield about 18 gallons of oil, but a much larger amount of sulphate of ammonia. The oil consists chiefly of members of the paraffin and olefine series, and thus differs essentially from that obtained from true coal-shales, in which the hydrocarbons of the benzene group are largely represented.
A full account of the Scotch shale-oil industry, as the most important and typical, will be given later, the corresponding industries in other countries and districts being dealt with first.
In addition to the Carboniferous oil-shales of Flint and Stafford, the Kimmeridge shale, a bluish-grey slaty clay, containing thin beds of highly bituminous shale, occurs in Dorsetshire, and has from time to time attracted attention as a possible source of shale-oil products. The so-called “Kerosene-shale” of New South Wales has been extensively mined, and the industry is now being developed by the Commonwealth Oil Corporation, Ltd. The French shale-oil industry is much older than that of Scotland, but has made far less progress, the amount of shale distilled in 1897 being 200,000 tons, as compared with 2,259,000 tons in Scotland. The shales of New Zealand have never been extensively worked, the production having decreased instead of increased. Oil-shale of good quality occurs in Servia, and has been found to yield from 431/2 to 541/2 gallons of oil per ton. The production of mineral oils and paraffin by the distillation of lignite is carried on in Saxony, the mineral worked being a peculiar earthy lignite, occurring within a small portion of the Saxon-Thuringian brown-coal formation. Other occurrences of this mineral have been indicated in the list of localities above.
The Shale-Oil Industry of Scotland.—The modern development of the shale-oil industry of Scotland dates from the commencement of Robert Bell’s works at Broxburn in 1862.
The oil-shales are found in the Calciferous Sandstone series, lying between the Carboniferous Limestone and the Old Red Sandstone. They occur at several points in the belt of Carboniferous rocks across the centre of Scotland, for the most part in small synclinal basins, the largest of which is that at Pentland, where the levels are 2 m. long, without important faults. Mining is carried on, where the seams are over 4 ft. thick, by the “pillar and stall” system; seams under 4 ft. are worked by the “longwall” system. The shale is blasted down by gunpowder, and passed over a 1-in. riddle, the smalls being left underground. Before being retorted the shale is passed through a toothed breaker, which reduces it to flat pieces 6 in. square. These fall into a shoot, and thence into iron tubs of 10 to 25 cwt. capacity, which run on rails to the tops of the retorts.
The retorts in which the shale is distilled have undergone considerable variation and improvement since the foundation of the industry. Originally horizontal retorts, like those used in the manufacture of coal-gas, were employed, and the heavy oils and paraffin were burned as fuel. When the latter product became valuable vertical retorts were adopted, as the solid hydrocarbons undergo less dissociation under these conditions. Steam was employed to carry the oil vapours from the retort. The earliest form of vertical retort was circular (2 ft. in diameter) or oval (2 ft. by 1 ft. 4 in.) and 8 or 10 ft. long. Six or eight of these were grouped together, and the heating was so effected that the bottoms of the retorts were at the highest temperature. They were charged by means of hoppers at the top, the exhausted shale being withdrawn through a water-seal every hour and fresh added, whence this is known as the “continuous system.”
In the first Henderson retort (1873) the spent shale was used as fuel. The retorts, which were oblong in cross-section, were arranged in groups of four, and had a capacity of 18 cwt. They were charged in rotation, as follows: when a sufficient temperature had been attained in the chamber containing them, one retort was charged from the top, and in four hours the one diagonally opposite to it was charged. After eight hours the one next to the first was charged, and after twelve hours the fourth. Up to the sixteenth hour only ordinary fuel was used in the furnace, but the spent shale from the first retort was then discharged into it. The other retorts were similarly discharged in the above order at intervals of four hours, each being at once recharged. The shale was black when discharged, but soon glowed brightly. Owing to the small amount of carbon in the spent shale, only a slow draught was kept up. The outlet for the oil vapours was at the lower and less heated end of the retorts, and steam, which had been superheated by passage through pipes arranged along one side of the retort chamber, was blown in copiously through pipes to aid in the uniform heating of the shale and to continuously remove the oil vapours, dissociation from overheating being thus minimized. It was believed that a temperature of about 800° F. produced the best results. This retort was worked on what is known as the “intermittent system.”
The Pentland Composite retort (1882) and the later Henderson type (1889) were both continuous-working and gas-heated, the second being a modification of the first, designed with a view to obtaining a larger yield of sulphate of ammonia without detriment to the crude oil. In both the upper part of the retort was of cast iron and the lower of fire-clay. The upper portion was heated to a temperature of about 900° F. whilst the lower was maintained at about 1300° F. The charge in the retort gradually travelled down, owing to the periodical removal of spent shale at the bottom, and the descent was so regulated that no shale passed into the highly-heated part until it had parted with the oil it was capable of yielding. The shale, however, still contained nitrogen, which in the presence of steam produced ammonia at the higher temperature.
The three classes of retorts now employed in the distillation of shale in the Scottish oil-works are covered by the following patents:—
1. In use at Pumpherston, Dalmeny and Oakbank—No. 8371 of 1894; No. 7113 of 1895; No. 4249 of 1897.
2. In use by Young’s Paraffin Light and Mineral Oil Company, Ltd.—No. 13,665 of 1897; No. 15,238 of 1899.
3. In use by the Broxburn Oil Company, Ltd.—No. 26,647 of 1901. The objects of the invention for which patent No. 8371 of 1894 was granted to Bryson (of Pumpherston Oil Works), Jones (of Dalmeny Oil Works), and Fraser (of Pumpherston Oil Company, Ltd.), are described in the specification as “to so construct the retorts and provide them with means whereby fluxing or dandering of the substance being heated is prevented in the retorts: also to effect an intermittent, continuous, or nearly so, movement within the retort.” In order to carry out these objects, the bottom of the ​ retort is provided with a disk or table to support the material within the retort. Above the table there is a revolving arm or scraper, by the action of which a portion of the material is continuously swept off the table and discharged into the hopper below. The column of material within the retort is thus caused to move downwards, and the tendency of the material to flux or dander is thereby prevented or reduced. In order to pulverize the material before reaching the hopper, teeth may be formed upon the lower part of the retort and upon the table, and the revolving scraper may be similarly toothed. A short revolving worm or screw may be substituted for the table or scraper. As a modification, the table may be made convex and provided on each side with rocking-arms connected together above the table by a cross-arm or scraper.
The principal object of the invention for which patent No. 7113 of 1895 was granted to the same applicants is stated to be such arrangement of the parts of the retort as results in the retort, after being heated and started, requiring “practically no fuel to keep it going, owing to the great amount of heat generated in the retort by means of the effectual decomposition of the carbon contained in the waste material by means of one or more jets of steam (which may be superheated) being passed into the retort as near the outlet or discharge-door of the retort as possible, thus utilizing all, or nearly all, the heat contained in the waste material within the retort, thus saving labour, time and expense, as well as wear and tear of the retort.”
The object of the invention for which patent No. 4249 of 1897 was granted to Bryson is stated to be “to so construct the hoppers of the retorts that one or more retorts can be drawn or discharged through one door, and also to provide simple and efficient means for operating the said door.”
Patent No. 13,665 of 1897 was granted to William Young and John Fyfe for an invention the objects of which are described in the specification in the following words: “To reduce labour, save fuel, and increase the products, and to enable existing but worn-out retorts that have been erected in accordance with the above invention to be economically replaced upon existing foundations by similar retorts, provided with improved and enlarged multiple hoppers for the reception of the shale to pass through the retorts, and also enlarged chambers for the reception of the ash or exhausted shale; the retorts being provided with mechanical arrangements for the continuous passage of the fresh shale into them from the multiple hopper, and the continuous discharge of the ash or spent shale into the receiving chamber. Those improved mechanical alterations in the structure of the retorts greatly reduce the manual labour, enabling most of the work to be done during the day, the multiple hopper and spent-shale chamber being of such dimensions as will supply fresh shale and receive the spent shale during the night-shift, the only labour then required being the supervision, regulating temperature of the retorts, and seeing that the mechanical arrangements are working properly.”
The multiple hoppers are constructed of mild steel plates with flat bottoms to which the retorts are bolted by flanges, the steel bottoms admitting of the differential expansion, to which the retorts are subject, taking place without damage to the retorts or hoppers. To ensure the shale regularly passing from the hoppers to the retorts, each hopper is provided with a rocking-shaft to which are attached rods or chains hanging into the mouths of the retorts, these rods or chains being thus made to rise or fall. The spent shale receiving-chambers at the lower end of each retort are of greatly enlarged size, and the lower end of each retort is provided with a mechanical device for the continuous discharge of the spent shale into these chambers. The improvements are stated to be specially applicable to retorts of the Young and Beilby (Pentland) type.
Patent No. 15,238 of 1899 was obtained by the same inventors for improvements designed to obviate objections found to attach to retorts constructed on the ordinary Young and Beilby system. In the use of such retorts, composed of an upper metallic section and a lower fire-brick section, with chambers or hoppers at their upper ends, these upper ends became gradually filled up with hard carbonaceous matter, and this necessitated the periodical stopping of the working to have such matter removed. Moreover, the shale residues became fluxed and fixed to the walls of the lower section of the retorts. The residues were further liable to pass through the retort in an imperfectly exhausted condition, and to pass more quickly down the front or side of the retort next the discharging door. It was also found that when air and steam were used difficulties arose in regulating the quantities and proportions of steam and air used to burn the carbon out of the shale residues while preventing obstructions due to fluxing of the residues. To overcome these drawbacks each retort is composed of four sections, viz. a hopper redistillation chamber at the top, a metallic section, a fire-brick chamber, and a combustion chamber of large capacity at the bottom. The combustion chamber is not externally heated, but receives the spent shale from the retort in a red-hot condition, and the further supply of heat in this chamber is wholly due to the burning of the carbon by the introduced air and steam, the danger of the fluxing and fixing of the shale residue to the walls of the chamber being thus minimized. To successfully burn the carbon remaining in the shale residue when it reaches the combustion chamber, so as to obtain the maximum yield of ammonia, careful regulation of the quantity and proportions of the air and steam is necessary, and a special device is provided for this.
The important construction of retorts for which patent No. 26,647 of 1901 was granted to N. M. Henderson of the Broxburn Oil Works, relates to such retorts as are described in the same inventor's previous patent, No. 6726 of 1889. The patentee dispenses with the chamber or space between the upper and lower retorts, the upper cast-iron retorts being carried direct on the upper end of the lower brick retorts, thus forming practically one continuous retort from top to bottom; and instead of one toothed roller being employed for the purpose of withdrawing the exhausted residue, a pair of toothed rollers is used for each retort, This improved construction is stated to give “better and larger results with less labour and expense in working and for repairs.”
The vapour from these retorts, amounting to about 3000 cub. ft. per ton, is partially condensed by being passed through 70 to 100 vertical 4-in. pipes, whose lower ends fit into a chest. About one-third of the vapour is condensed, the liquid, consisting of about 75% of ammoniacal liquor and 25% of crude oil, flowing into a separating tank, whence the two products are separately withdrawn for further treatment. Part of the uncondensed gas is sometimes purified and used for illuminating purposes, when it gives a light of about 25 candlepower. The remainder is used as fuel, usually after compression or scrubbing to remove all condensable vapours.
Crude shale-oil is of dark green colour, has a specific gravity 0·860 to 0·890, and as at present manufactured, with the newer forms of retorts, has a setting point of about 90° F. It contains from 70 to 80% of members of the paraffin and olefine series, together with bases of the pyridine series, and some cresols and phenols. Beilby states that average Scotch shale-oil contains from 1·16 to 1·45% of nitrogen, mainly removable by sulphuric acid of specific gravity 1·220, and mostly remaining in the pitchy residues left on distillation. The lightest distillate, known as naphtha, contains from 60 to 70% of olefines and other hydrocarbons acted upon by fuming nitric acid, and the lubricating oils consist mainly of olefines. The paraffin wax chiefly distils over with the oil of specific gravity above 0·840.
In the refining of crude shale-oil, the greatest care is exercised to prevent dissociation of the paraffin, large volumes of superheated steam being passed into the still, through a perforated pipe, at a pressure of from 10 to 40 ℔, to facilitate distillation at the lowest possible temperature. The original system of intermittent distillation is now employed only at the works of Young's Company. The stills have cast-iron bottoms and malleable-iron upper parts, their former capacity being 1200 to 1400 gallons, but those now made usually holding 2000 to 2500 gallons. Each still has its own water-condenser, the flow of water being regulated according to the nature of the distillate. The usual condensing surface is 230 ft. of 4-in. pipe. The process now in general practice is, with slight variations, the Henderson system of continuous distillation (patent No. 13,014 of 1885). It consists of a primary wagon-still, connected with two side-stills, which are further connected with pot-shaped coking-stills. The oil is heated in feed-heaters by the gases evolved from the hottest still before passing into the first still, where the temperature is so regulated as to drive off only naphtha up to about 0·760 specific gravity. The heavier portion of the oil passes to the other stills, the outermost receiving the heaviest only.
In both these systems the naphtha is collected separately, while the remainder of the distillate, known as “once-run oil,” is condensed without fractionation. This “once-run oil” is treated with sulphuric acid and alkali at a temperature of 100° F. in agitators of varying construction—some being horizontal cylinders with a shaft carrying paddles, while others take the form of vertical cylindrical tanks with egg-shaped bottoms—in which agitation is produced by means of compressed air. The loss of oil during the agitation is estimated at 1·5 to 2·0%.
The oil is next fractionated, either by the intermittent or the continuous system. After the most volatile fractions have distilled off, steam is blown in through a pipe at the bottom of the still. In many cases the distillate, with a density up to ​ 0·770, constitutes the crude naphtha, and that up to a density of 0·850 the burning oil. The remainder of the distillate, which solidifies at common temperatures, consists chiefly of lubricating oils and paraffin. These three fractions are delivered from the condensers into separate tanks. Although the crude-oil stills of Henderson may be employed for the continuous distillation of the once-run or other oils obtained in the process of refining, the inventor prefers another form of apparatus which he patented in 1883 (No. 540), and this is now generally used. This consists of three horizontal cylindrical stills, 7 ft. in diameter and 19 ft. in length. The oil enters through a pipe which passes through one end of the still and discharges at the opposite end, while the outlet-pipe is fitted below the inlet-pipe at the bottom of the end through which the latter passes, inlet and discharge being thus as far as possible from each other. The oil circulates as in the crude-oil stills. The burning oil is next treated with acid and alkali, and subsequently again fractionally distilled, the heavier portion yielding paraffin scale, while the residues are redistilled. The final chemical purification of the burning oil resembles that last referred to, but only half the quantity of acid is employed. The lighter products of these distillations form the crude shale naphtha, which is treated with acid and alkali, and redistilled, when the lightest fractions constitute the Scotch “gasoline” of commerce, and the remainder is known as “naphtha.”
The solid paraffin, which is known in its crude state as paraffin scale, was formerly produced from the heavy oil obtained in the first, second and third distillations, that from the first giving “hard scale,” while those from the second and third gave “soft scale.” The hard scale was crystallized out in shallow tanks, and the contained oil driven out by compression of the paraffin in filter bags. Soft scale was obtained by refrigeration, cooled revolving drums being caused to dip into trays containing the oil, when the paraffin adhered to the drums and was scraped off by a mechanical contrivance. Later improved appliances have aimed at the slow cooling of oil in bulk, whereby large crystals of paraffin are produced. Several processes have been invented, the most generally used being that patented by Henderson (No. 9557 of 1884). His cooler consists of a jacketed trough having a curved bottom, and divided into a series of transverse casings by metal disks, each consisting of two thin plates bolted together, but with a space between, in which, as also in the jacket surrounding the trough, cold brine is circulated. The paraffin crystallizes on the cold surfaces, from which it is constantly removed by scrapers, so that successive portions of the oil are cooled. The solid paraffin accumulates in a well or channel, where it is stirred up by rotary arms, so that it may be readily drawn away by a pump to the filter-press, whereby the solid paraffin is freed from oil. In the improved process of cooling employed at the works of the Oakbank Oil Company the oil to be cooled is pumped through coils submerged in the expressed oil from the filter-presses into the inner space of vertical coolers formed of two cast-iron tubes, and thence direct to the filter-presses. In the inner chamber of the coolers are fitted revolving scrapers, while in the outer annular space compressed ammonia is expanded.
The crude paraffin is then refined, for which purpose the “naphtha treatment” was formerly employed, but this has now given place almost entirely to the “sweating process.” In the former the paraffin is dissolved in naphtha and then crystallized out. The sweating process consists in heating the crude wax to such a temperature that the softer portions are melted and flow away with the oil. In the process patented by N. M. Henderson (Nos. 1291 of 1887 and 11,799 of 1891), a chamber, 52 ft. by 13 ft. by 10 ft. high, heated by steam-pipes, and provided with large doors and ventilators for cooling, is fitted with a number of superimposed trays, 21 ft. by 6 ft. by 6 in. deep. These rest on transverse heating pipes, and each tray has a diaphragm of wire gauze. The bottoms communicate with short pipes fitted with swivel nozzles, worked on a vertical shaft. The diaphragms are covered with 1/2 in. of water, and the crude paraffin is melted and pumped through charging-pipes on to its surface. When the paraffin has solidified, the water is drawn off, leaving the cake resting on the gauze. Doors and ventilators are then closed, and the chamber is heated, whereupon the liquefied impurities are drained off until the outflowing paraffin sets on a thermometer bulb at 130° F. The remainder is melted and decolorized by agitation with finely powdered charcoal. The charcoal is mainly separated by subsidence, and the paraffin drawn off into filters, whence, freed from the suspended charcoal, it runs into moulds, and is thus formed into cakes of suitable size for packing. The lubricating oils are refined by the use of sulphuric acid and alkali, substantially in the same manner as the burning oils.
The following table shows the average yield, in 1895, of the various commercial products from crude shale-oil at two of the principal Scottish refineries. The percentages are, however, often varied to suit market requirements:—
Young’s Paraffin Light and Mineral Oil Co. :
| Gasoline and naphtha | Gasoline and naphtha | 6·09 |
| Burning oils | Burning oils | 31·84 |
| Intermediate and heavy oils | Intermediate and heavy oils | 23·97 |
| Paraffin scale | Paraffin scale | 13·53 |
| Total | Total | 75·43 |
| Loss | Loss | 24·57 |
| | | 100·00 |
| Broxburn Oil Co. |||
| Naphtha | | 3·0 |
| Burning oil | 30·0 |
| Gas oil | 9·0 |
| | —— | 39·0 |
| Lubricating oil | | 18·0 |
| Paraffin | | 10·0 |
| Loss | | 30·0 |
| | | 100·0 |
From the ammoniacal liquor the ammonia is driven off by the application of heat in stills, the evolved vapour being conducted into “cracker-boxes,” which are now usually of circular form, from 5 to 8 in. in diameter, and 6 to 12 in. in depth. In these boxes the ammonia is brought into contact with sulphuric acid of about 50° Tw., and is thus converted into sulphate. Wilton’s form of cracker-box, which is now generally in use, is provided with an arrangement for the automatic discharge on to a drying table of the sulphate of ammonia as it is deposited in the well of the box, and the process is worked continuously. For the heating of the ammoniacal liquor the ordinary horizontal boiler-stills formerly used have been superseded by “column-”stills, in which the liquor is exposed over a large area, as it passes from top to bottom of the still, to the action of a current of steam. (B. R.)
Paraffin, in chemistry, the generic name given to the hydrocarbons of the general formula C$_𝑛$H$_{2𝑛+2}$. Many of these hydrocarbons exist as naturally occurring products, the lower (gaseous) members of the series being met with as exhalations from decaying organic matter, or issuing from fissures in the earth; and the higher members of the series occur in petroleum (chiefly American) and ozokerite. They may be synthetized by reducing the alkyl halides (preferably the iodides) with nascent hydrogen, using either sodium amalgam, zinc and hydrochloric acid, concentrated hydriodic acid (Berthelot, Jour. prak. Chem. 1868, 104, p.103), aluminium amalgam (H. Wislicenus, ibid., 1896 (2), 54) or the zinc-copper couple (J. H. Gladstone and A. Tribe, Ber., 1873, 6, p. 202 seq.) as reducing agents.
They may also be derived from alkyl halides by heating to 120–140° with aluminium chloride in the proportion of three molecules of alkyl halide to one molecule of aluminium chloride (B. Köhnlein, Ber., 1883, 16, p. 560); by heating with zinc and water to 150–160° C. (E. Frankland, Ann., 1849, 71, p. 203; 1850, 74, p. 41), 2RI+2Zn+2H$_2$O＝2RH+Znl2+Zn(OH)$_2$; by conversion into zinc alkyls, which are then decomposed by water, ZnR$_2$+2H$_2$O＝2RH+Zn(OH)$_2$; by conversion into the Grignard reagent with metallic magnesium and decomposition of this either by water, dilute acids or preferably ammonium chloride (J. Houben, Ber., 1905, 38, p. 3019), RMgI+H$_2$O＝RH + Mgl(OH); by the action of potassium hydride (H. Moissan, Comptes rendus, 1902, 134, p. 389); and by the action ​of sodium, in absolute ether solution (A. Wurtz, Ann. chim. phys., 1855 (3), 44. p. 275), 2RI+2Na＝R·R+2NaI. They may also be obtained by the reduction of the higher fatty acids with hydriodic acid (F. Krafft, Ber., 1882, 15, pp. 1687, 1711), C$_𝑛$H$_{2𝑛}$O$_2$+6HI＝C$_𝑛$H$_{2𝑛+2}$+2H$_2$O+3I$_2$; by the conversion of ketones into ketone chlorides by the action of phosphorus pentachloride, these being then reduced by hydriodic acid,
C$_𝑛$H$_{2𝑛+1}$$_2$CO→C$_𝑛$H$_{2𝑛+1}$CCl$_2$→C$_𝑛$H$_{2𝑛+1}$$_2$CH$_2$;
by the reduction of unsaturated hydrocarbons with hydrogen in the presence of a “contact” substance, such, for example, as reduced nickel, copper, iron or cobalt (P. Sabatier and J. B. Senderens, Ann. chim. phys., 1905 [8], 4, pp. 319, 433); by the elimination of carbon dioxide from the fatty acids on heating their salts with soda-lime or baryta, CH$_3$CO$_2$Na + NaOH＝CH$_4$+Na2CO$_3$, or by heating their barium salts with sodium methylate in vacuo (I. Mai, Ber., 1889, 22, p. 2133); by the electrolysis of the fatty acids (H. Kolbe, Ann., 1849, 69, p. 257), 2C$_2$H$_4$O$_2$＝C$_2$H$_6$+2CO$_2$+H$_2$O; and by the action of the zinc alkyls on the ketone chlorides, (CH$_3$)$_2$CCl$_2$ + Zn(CH$_3$)$_2$＝C$_5$H$_{12}$+ZnCl$_2$.
The principal members of the series are shown in the following table:—
The lowest members of the series are gases at ordinary temperature; those of carbon content C$_5$ to C$_{15}$ are colourless liquids, and the higher members from C$_{15}$ onwards are crystalline solids. The highest members only volatilize without decomposition when distilled under diminished pressure. They are not soluble in water, although the lower and middle members of the series are readily soluble in alcohol and ether, the solubility, however, decreasing with increase of molecular weight, so that the highest members of the series are almost insoluble in these solvents. The specific gravity increases with the molecular weight but always remains below that of water. The paraffins are characterized by their great inertness towards most chemical reagents. Fuming sulphuric acid converts the middle and higher members of the series into sulphonic acids and dissolves the lower members (R. A. Worstall, Amer. Chem. Journ., 1898, 20, p. 664). Dilute nitric acid, when heated with the paraffins in a tube, converts them into secondary and tertiary nitro-derivatives (M. Konowalow, Ber., 1895, 28, p. 1852), whilst long boiling with strong nitric acid or nitro-sulphuric acid converts the middle and higher members of the series partly into primary mono- and di-nitro compounds and partly oxidizes them to carbonic, acetic, oxalic and succinic acids (Worstall, ibid., 20, p. 202; 21, p. 211). Fuming nitric acid only reacts slowly with the normal paraffins at ordinary temperature, but with those containing a tertiary carbon atom the reaction is very energetic, oxidation products (fatty acids and dibasic acids) and a small quantity of polynitro compounds are obtained (W. Markownikow, Centralblatt, 1899, 1, p. 1064; Ber., 1899, 32, p. 1441). Chlorine reacts with the paraffins, readily substituting hydrogen. Isomeric hydrocarbons in this series first appear with butane, the number increasing rapidly as the complexity of the molecule increases. For a means of determining the number of isomers see E. Cayley, Ber., 1875, 8, p. 1056; F. Hermann, Ber., 1898, 31, p. 91.
For Methane see Marsh Gas. Ethane, C$_2$H$_6$, occurs in crude petroleum. It may be prepared by the general methods given above; by heating mercury ethyl with concentrated sulphuric acid (C. Schorlemmer, Ann., 1864, 132, p. 234); or by heating acetic anhydride with barium peroxide (P. Schützenberger, Zeit. für Chemie, 1865, p. 703), 2(CH$_3$CO)2O+BaO$_2$＝C$_2$H$_6$ + Ba(C$_2$H$_3$O$_2$)$_2$+2CO$_2$. It is a colourless gas which can be liquefied at 4° C. by a pressure of 46 atmospheres. By slow combustion it yields first water and acetaldehyde, which then oxidizes to oxides of carbon and water (W. A. Bone; see Flame), whilst in ozonized air at 100° it gives ethyl alcohol, together with acetaldehyde and traces of formaldehyde (Bone, Proc. Chem. Soc, 1904, 29, p. 127).
Dimyricyl (hexacontane), C$_{60}$H$_{122}$, is prepared by fusing myricyl iodide with sodium (C. Hell and C. Hägele, Ber., 1889, 22, p. 502). It is only very slightly soluble in alcohol and ether.