V.—The comparative value of different methods of fractional distillation

Frederick D. Brown
1880 Journal of the Chemical Society Transactions  
WHERE fractional distillation is carried out on a large scale, carious forms of a p p r a t u s of a somewhat complicated character are generally employed ; though differing much in detail they are all clesigued to subject tlie mixed vapours to one or both of two well defined processes, which for the purposes of this paper may be termed respectively L V I L S~~~ and cooZi?rg. In the process of washing, the mixed vapours issuing from the still are made to pass through sevei-a1 layers of liquid
more » ... layers of liquid obtained by their own partial condensation, they are thus washed by these successive layers, and it is supposed that the vapour of the liquid of highest boiling point is partially removed by this process, which results therefore in a distillate containing more of the liquid of lo\T-er boiling point than would be obtained by simple distillation. There is a t first sight, however, no reason t o suppose that a mixture of vapours should be materially altered in composition by a liquid having about the same composition and the same temperature as itself. It would appear that the first step iii the construction of these forms of apparatus resulted from an attempt to utilise the latent heat! of the vapour given off by a weak spirit to distil R stronger one ; the latent heat of the vapour of this second spirit might then be used t o distil a third, and so on, thus effecting a series of distillations in the same apparatus with the same fuel. If this series of distillations actually took place, that is to say, if the ~a p o u r s rking from the still really voi. XXXTIl. E:
doi:10.1039/ct8803700049 fatcat:2mljambivfaefgjj5wcyh6fwlm