— 158 — 



It may be said that steam, just as air or other indifferent gases, when 

 used as an evaporating-agent, plays the part of an air-pump. 



In theory, therefore, water-distillation should be able to separate a 

 mixture of liquids insoluble in water just as readily as is done by distil- 

 lation without water at the same steam-temperature. But in practice it 

 is found, ceteris paribus, that the separation-effect obtained with water- 

 distillation is not so good, because when a fractionating head (or, in 

 working on a large scale, a column) is used, the exchange of the vapour 

 mixture with the condensate (which is the determining factor when frac- 

 tionating the oil-vapour), is disturbed and impeded by the quantities of water 

 which are admixed with the oil and which in some cases overlay it. This is 

 the reason why low-boiling mixtures of liquids are more readily separated 

 by water-distillation than are less volatile mixtures: a fact which has 

 also been observed by Golodetz. For in the case of the first-named mix- 

 tures the condensed steam contains comparatively little water, but in 

 the case of the latter it contains a great deal. For example, 1 kilo steam, 

 when boiling takes place at atmospheric pressure, is capable of evaporating 

 9,11 kilos benzene or 5,82 kilos toluene, but only 0,18 kilos nitrobenzene 

 or 0,05 kilos naphthalene. 



Our Report of October 1910 contained a paragraph (p. 167) relating 

 to a paper by Auwers and Roth on the thermic value of various terpene- 

 bodies. Soon after the publication of this paper the authors' attention 

 was drawn to a slight experimental error, owing to which the ascertained 

 values had been slightly below the actual. Auwers, Roth and Eisenlohr 1 ), 

 however, have found that the theoretical conclusions which they had drawn 

 from their previous experiments are in no way affected by the increase 

 of the separate values. 



A paper by Auwers and Moosbrugger 2 ) on the refraction and dis- 

 persion of organic substances 3 ) with several double linkings contains data 

 concerning the dispersion and refraction-values of a series of alicyclic 

 dienes 4 ) and other oxygenated compounds of an analogous constitution. 

 The commonly accepted theory that all these compounds are spectro- 

 chemically normal is in essence based upon conclusions of analogy which 

 rest upon a very weak experimental foundation. 



Examined spectrochemically the bodies under review showed no 

 tendency towards exaltation either in their index of refraction or of di$; 

 persion. 



x ) Liebigs Annalen 385 (1911), 102. 



2 ) Liebigs Annaien 387 (1912), 167. 



3 ) Comp. Report October 1911, 122. 



4 ) Dienes, according to the Geneva nomenclature, are hydrocarbons with 2 double bonds. 



