832 



finall J disfillation over metallic Ca. We have further ascertained 

 that on fractionated distillation with Hahn's still-head (1910) this 

 alcohol did not jield fractions of different specific gravity', the best 

 criterion that actually all the water had been removed. 



We had further an opportunity to compare alcohol derived from 

 two different sources viz. from the "Supra-grain spirit" and the 

 "Prime Grain (\/,) and Molasses ('/,) mixed", both originating from 

 the Delft Yeast and Spirit Works. Mendelejeff only accurately 

 determined the specific gravity of the absolute alcohol from grain 

 spirit. Our investigation has revealed that in this respect there is 

 no difference with molasses spirit. 



Besides we were enabled to use a more accurate method for the 

 determination of the specific gravity than earlier investigators by the 

 application of the picnometer given by Johnston and Adams for the 

 determination of the specific gravity of solid substances. Through 

 the way of closure of this picnometer with a plane ground closing 

 cover the error of the meniscus formation is entirely obviated, no 

 correction needing to be applied for the weight of the vapour of 

 the examined substance, which fills the space between liquid. mirror 

 and stopper otherwise. We used such a picnometer of somewhat 

 more than 100 cm., filled it immediately at the mouth of the 

 still-head with exclusion of the moisture from the atmosphere, 

 and applied the corrections in the weighings for the reduction to 

 vacuum. Thus the measurements could be made accurate to the 

 fifth figure of decimals of the specific gravity, in which as chief 

 source of error remained the accurate adjustment of the temperature. 

 This must take place with an accuracy of 0,01° in the thermostat, 

 for in consequence of the great coefficient of expansion of alcohol 

 a difference of 0.01° corresponds with a difference of about 0,00001 

 in the specific gravity. But besides, the thermometer which is used 

 for the determination of these temperatures, must agree down to 

 0,01° with the international hydrogen scale. We were not quite sure 

 about this last point, because we had only an opportunity to compare 

 our thermometer with the best, but pretty old standard thermometer 

 of the Metereological Institute at De Bilt. 



Our results for specific gravity ^ (1.1.) of alcohol are the following: 

 (See table on the following page). 



Comparison of the specific gravity of absolute alcohol immediately 

 after the last distillation over calcium and saturation with dry air, 

 and also after the gases dissolved at the airpump had been boiled out 



before the boiling out 0,79360 



after the boiling out 0,79362 



