592 



NAPHTHA, COAL 



The fluid hydrocarbons boiling above this point have not been well studied. 

 Ordinary coal-naphtha, in addition to the above hydrocarbons, contains traces of the 

 homologues of olefiant gas, alluded to in the article NAPHTHA. 



All the above-mentioned hydrocarbons may be separated from each other by 

 careful and sufficiently numerous fractional distillations. It is proper before con- 

 sidering them as pure, to shake them up several times with oil of vitriol, and, after 

 well washing first with water, and afterwards with an alkaline solution, to dry them 

 very carefully with chloride of calcium or sticks of potash. It will be observed that 

 in the above table the specific gravities of the hydrocarbons are not in harmony ; 

 this arises from the fluids upon which the experiments were made not having all been 

 procured from the same source ; for it has been found that the same bodies, as pro- 

 cured from different sources, often present small but appreciable differences in 

 odour, density, boiling-point, and other physical properties. 



The benzole of coal-naphtha may almost entirely be separated by distilling in an 

 apparatus first devised for the purpose by Mr. C. B. Mansfield. The annexed figures 

 from G. Williams's ' Handbook of Chemical Manipulation,' illustrate the vessels he 

 employed for the purpose. Fig. 1545 consists of a copper or tinned iron still, a, 

 holding about two gallons. The flange b b, is merely to support the apparatus in the 

 ring of a gas or charcoal furnace, preferably the former. A wide worm, c c, passes 

 through the top of the still into a water-tight cistern, d d. The worm ends in a 

 discharge-pipe, e. The latter is to be attached to a common worm tub containing 

 cold water. The crude benzole, or coal-naphtha, is to be placed by means of the 

 opening/ into the still, and all the joints of the apparatus being closed, and effectual 

 condensation insured, the fire is to be lighted. The naphtha soon begins to boil, but 

 nothing comes over, because the water in d d effects condensation. In a short time, 

 however, the water in d d begins to get warm, and, as soon as 177 is reached, 

 benzole begins to come over, and is perfectly condensed in a second worm, kept cold 

 by means of water. It is plain that as the fluids of higher boiling-points begin to 

 come over, the water in d d will boil, but distillation then ceases entirely. The 

 reason of this is, that nothing can make the head c c hotter than 212, because of its 

 being surrounded with water. All hydrocarbons that are not volatile at 212 are 

 consequently condensed there, and fall back into a. The benzole distilling over is 



1545 1546 



quite pure enough for all ordinary purposes. It may, if required very pure, be rec- 

 tified a second time in the same apparatus, taking care that the head does not get 

 hotter than 180 or 190. If the benzole is wanted absolutely free from its accom- 

 panying hydrocarbons, it must be purified by freezing. For this purpose the rec- 

 tified benzole is to be placed in a thin glass or metal vessel, and surrounded with 

 snow or pounded ice mixed with salt. The whole apparatus is to be surrounded 

 with sawdust and covered with woollen cloths to prevent access of heat. As soon as 

 the benzole is frozen, it is to be placed in a funnel and allowed to drain. The solid 

 mass when thawed is pure benzole. By this mode of proceeding, a considerable quan- 

 tity of fluid is always accumulated, which refuses to freeze and yet boils at the proper 

 temperature for benzole. G. Williams found it to contain a small quantity of the 

 OH" series of hydrocarbons (homologous with olefiant gas). Mr. Cliurch states it 

 to contain benzole in a peculiar condition ; ho calls it parabenzole. The presence of 

 the OH" series may always be proved by the readiness with which the fluid de- 

 colourises bromine-water. 



A similar form of apparatus for rectifying benzole, and one that answers almost as 

 well, js that represented in fig. 1546. It will be seen that the worm c c of Jiff. 1545 is 

 replaced by a straight tube. The mode of use is precisely the same. 



Whore the benzole is to be extracted from coal-naphtha on the large scale, the 

 following apparatus will be found convenient: The boiler a a, fig. 1547, surrounded 



