( 1^4 ) 



KoHNSTAM.M ^) lias prox'Cfl tlijit llio way iii wliicli those liltlc (ul)es 

 are filled, may give rise to ei-rors in the deteriniiialioii of the vapour 

 pressure, even when they are filled with a simple substance, and 

 not as with Cunaeus with a mixture. '^} 



2"^l By adjusting a glass spiral lietween the globe in which the 

 liquid was brougiit and the experimental tube the globe could be 

 violently shaken, which {)revented insufficient mixing of the layers of 

 the liquid. 



3''f^. The difference in appearance between successive fringes was 

 very slight with Cunaeus, which rendered the adjustment of the 

 movable interference phenomena compared with the firm, pretty un- 

 certain. By taking a more favourai)le relatioii of the distance between 

 two corresponding edges of the slits to the width of each of those 

 slits, spectra were distinctly visible on the sides of the bands, all 

 turning their violet rim to the middle fringe. So there was a means 

 of ascertaining the latter. 



Moreover it was investigated whether possible absorption of vapour 

 on the [)lates of plate glass would have influence on the course of 

 the ^Ai'-curves. This appeared not to be the case, however, so that 

 this was no longer done in the examination of the second mixture. 



The temperature at which the substances were examined, was 0°C. 



The substances were obtained from KAin-BAUM at Bei'lin and were 

 purified before use by distillijig them a few times by means of 

 a YorN(; and Tuomas' •') dephlegmator with twelve constrictions. 



The mixture acetone-ethyl etl Lev. 



The results of the experiment are stated in Table I. (p. lt)5). For the 

 refractivity that of dry air free from carbonic acid has been taken 

 as unity, the pressure is given in mm. of mercury at 0°C. Ethylether 

 must be considered as admixture. 



The i>.i\ ,r.^ diagram obtained in this way is graphically repre- 

 sented in fig. 1. 



From the course of the curves appears: There is a maximum 

 pressure, just on the side of the ether. 



The point of inflection" found by Cunaeus is also found liere, and 

 at about .v.2 = 0,66. 



1) IvoHxsTAMM, Proefschrift, Amsterdam, 1901, biz. 170—180. 



-) How dillicult it is to get tlie substance pure and free from air has been lately 

 observed once more by Teichner, Ann. de Phys. 13 p. 603. 



•') Sydney Young and Thomas, A dephlegmator for fractional distillation. Clieni. 

 News, 71, biz. 177. 



