— 155 — 



nevertheless forms no compound. But an additive compound which has 

 f a lower b. p. and at the same time a higher steam-pressure than its com- 

 ponents is scarcely imaginable, and as a matter of fact has not yet been 

 discovered. Probably the true explanation of the homogenous mixtures 

 with minimum boiling point is to be found rather in conceiving them as 

 transition-members between the heterogenous mixtures and the solutions 

 proper. From an optical standpoint it is true that they are solutions, but 

 for the rest their minimum boiling-point connects them more nearly with 

 the mixtures of mutually insoluble or sparingly soluble substances. 



2. "On fractional distillation in the laboratory and on new rectifying 

 apparatus" 1 ). A. Golodetz here deals with the course of the process of 

 fractional distillation of mixtures and with the conditions which should 

 govern the construction of distilling-apparatus for laboratory use. He 

 begins by explaining the familiar forms of such apparatus and then pro- 

 ceeds to explain a new model of fractionating-head, wich he calls the 

 "birectifier". We reproduce below the result of a trial distillation with 

 this apparatus. The charge consisted of equal parts of benzene and 

 toluene, and the steam-pressure was 746,5 mm. 



Temp. -Interval Quantity of Distillate 



79,42 to 79,6° 42 °/ 



79,6 „ 80,40 3)95 o/ o 



80,4 „ 81,4° 1,7 % 



81,4 „ 83,4° 0,8 % 



83,4 „ 86,4° 0,45 °/ 



86,4 „ 89,4° 0,35% 



89,4 „ 95,0° 0,43% 



95,0 „ 100,5° 0,72% 



100,5 „ 103,5° 0,95% 



103,5 „ 106,5° 0,98 % 



106,5 „ 108,5° 2,85% 



108,5 „ 109,3° 4,25% 



Toluene (from the difference) 40,85 % 



The first and the last fraction might be regarded respectively as al- 

 most pure benzene and toluene. 



For purposes of comparison the author has distilled quantities of 

 100 g. each of a single sample of turpentine oil in his own and in six 

 other distilling-heads. In the details of these experiments no mention is 

 made of the pressure, and whether in all the experiments it was preci- 

 sely, and not only approximately the same. The action of a fractionating 

 apparatus depends in the first place upon the pressure. 



!) Chem. Industrie 35 (1911), 102 and 141. 



