In the years 1860 and 1864 long and costly litigations as to the validity of Mr.Young's patent took place in Edinburgh and London, resulting in the main in his favor. Many years ago Reichenbach had. by distilling 100 lbs. of pit-coal, obtained nearly 2 oz. of an oily liquid exactly resembling natural naphtha; and various other chemical writers were appealed to, as proving that methods substantially the same as Mr. Young's were pre viously known and practiced. One thing seeme to have been admitted, that previous to his patent no one had succeeded in producing the oil on a commercial scale.
The processes by which the oil and paraffin are obtained are simple. The material best adapted for the purpose was for years believed to be Boghead coal, a very rich gas coal, occurring in a field cf limited extent near Batligate, in Linlithgowshire. All cannel coals, however, give the same products, and some of them in nearly as large quantity; but, as stated below, shale is now generally used and treated in the same way. The coal is broken into fragments like road-metal, and gradually heated to redness in east-iron retorts, which are similar to those used for coal-gas (see Gas). The retorts are most usually upright, about 10 ft. long and 14 in. in diameter at the bottom, tapering to 12 in. at the top, and built in sets of 3, 4, or 6, so that one fire may heat each set. The coal is fed by means of a hopper on the top of the retort, and after passing through it at a low red-heat, is drawn ont as coke at the bottom, where there is a water lute to pre vent the escape of oil or gas. - Thereis aspherieal valve in the hopper, counterpoised with a weEtht, which closes the retort at the top. The volatile matters distilled from the coal are conducted by a pipe to the condensers (similar to those used for where they are condensed into a thick black oil, of a specific gravity of about 0.900, along with a little water. Great care is necessary to prevent the heat from becoming too high, because gas and gas-tar, and not paraffin oil, are obtained when coal or shale is Instilled at a high temperature. A. ton of Boghead coal gave about 120 gallons of crude oil.
The crude oil from the first distillation is then distilled again in long cylindrical mal leable-iron stills. From this second distillation a "green oil" is obtained, and the residue is removed as coke from the bottom of the still. This oil is then mixed with from 5 to
10 per cent pf sulphuric acid, and afterwards with about the same quantity of soda, the mixtures being inade in circular tanks with revolving stirrers. Both the acid and the soda mix with impurities, which fall to the bottom as heavy tarry matters, and are run off be it stop-cock, till only the clear supernatant oil remains. After being so far purified, the oil undergoes three further distillations, being at the same time treated with strong acid (1 per cent) and soda. The final result is that a small quantity of light naphtha is obtained in the later distillations, three-fourths of what is left being a light and nearly colorless oil used for burning in lamps,6 and the, remainder a thicker oil containing paratilae. This latter portion is pressed in a hydraulic press, which squeezes out the greater portion of the paraffine, leaving an oil which is sold for lubricating machinery.
The crude paraffine, after being subjected to hydraulic pressure three or four times, is chiefly purified, by repeated crystallizations, from naphtha. Steam is afterwards blown through it in a incited state, and when finally treated with 3 per cent of animal char coal it is an exquisitely beautiful substance, resembling the purest white wax. It is largely manufactured into candles, which equal, or even excel, in appearance those made from wax, and are only about half as costly. Parafline has now a number of curious minor applications.
Shale naphtha. or "shale-oil," is a substance which has been manufactured, for many years, from bituminous shales, both in England and on the continent. Parly because the Boghead coal has become practically exhausted, but chiefly because the volatile prod ucts from it are more easily purified than from any coal, beds of bituminous shale found in the carboniferous formation are now almost entirely used in Scotland as the raw material from which paraffine oil and paraffine are obtained. Previous to 1850 these shales were turned to no account. See SHALE.
Naphtha from caoutehouc, itr enoutchine, is obtained from caoutchouc by destructive distillation. In composition it consists mainly of hydrocarbons, having the same pro portion of carbon to hydrogen as india rubber. Caoutchiue has the reputation of being one of the best known solvents for india rubber.