— 157 — 



have given better results for fractionation without the aid of water as an 

 evaporating- agent. Golodetz should have made the comparative test him- 

 self, using the same fractionating-head, and with the same rate of speed 

 in distilling, and the same distilling temperature. For the separation of 

 a mixture of vapours also depends, among other things, upon the extent 

 of the partial condensation in the fractionating-head. In the well-known 

 forms of fractionating-heads, as used in laboratory-work, and also in his 

 own "birectificator", there takes place a process known as "wild dephleg- 

 mation", i. e. a process of condensing induced by the cooler outer air 

 which defies regulation, and, this being so, the degree of steam-tempera- 

 ture, given equal heating, is also a factor in determining the measure of 

 separation. 



The other distilling-experiments of Golodetz also fail to bear out his 

 assertion that fractional distillation with water yields better results than 

 does ordinary distillation. He distilled a mixture of amyl formiate and 

 amyl acetate with water, and obtained an excellent separation-effect, but 

 he has not made any comparative distilling-experiment without water. 



On p. 641 of his treatise the author states that fractional distillation 

 by steam is quite a recent practice in essential oil chemistry. This as- 

 sertion would be correct if he had added the words "in the public labora- 

 tories'', for this mode of fractionation has been in use in the essential oil 

 industry for the past half century or so. 



In the course of our numerous comparative experiments, some of 

 which have been published 1 ), we have found that where the separation 

 of homogenous mixture of liquids is concerned, distillation by water is 

 less effective than dry distillation in cases where the mixture is not 

 at all or only slightly soluble in water. But where one of the components 

 of the mixture is soluble in water, that component is impeded, in water- 

 distillation, in proportion to its degree of solubility in the evolution of 

 steam. The component being thus kept back during the process, water- 

 distillation in this particular instance gives an excellent fractionation, in 

 particular when carried out with a fractionating-head. 



In the process of water-distillation of mixtures of liquids which are 

 not soluble in water to any extent, the steam only participates in the 

 formation of vapour to this extent that, while it is passing through, an 

 oil-free space is created into which the oil-mixture immediately commences 

 to pour its vapour, until saturation-point has been reached. The steam 

 'ktermines the extent of the generation of vapour from the oil-mixture, 

 but it does not influence the percentage of the oil-vapour. This is pre- 

 cisely the same as that of the saturated oil-vapour which rises from the 

 same oil-mixture at the same temperature when no water is present. 



1 ) v. Rechenberg, Theorie der Gewinnung und Trennung der athej-ische?i Ole durch 

 Destination. Grundziige einer allgemeinen Destillationslehre. 1910, p. 383. 



