of Dilute Solutions of Cane- Sugar and Ethyl Alcohol. 389 



necessarily uncertain correction to eliminate the effect of stir- 

 ring. The water containing the ice was allowed to remain in 

 the bath until the thermometer rose to a point at which it stood 

 constant for from five to ten minutes. About half an hour 

 elapsed from the time that the first ice separated until the 

 final reading was taken on the thermometer. A second 

 determination of the freezing-point of the water was then 

 made, just as the first had been. The thermometer used in all 

 of this work was the one already described"* as of the Beck- 

 mann type, and divided directly into thousandths of a degree. 

 Knowing the freezing-point of the water on the thermometer, 

 the vessel containing it was removed from the bath, the ice 

 melted, and then a measured volume of the water pipetted 

 off. An equal volume of a one-half normal sugar solution, 

 which had been prepared only a few hours, was then added. 

 This new dilute solution of sugar was thoroughly stirred, and 

 its freezing-point determined in all respects as that of the 

 water, as described above. The time required for a complete 

 determination of the lowering of the freezing-point of water 

 produced by a sugar solution being from 12 to 16 hours, 

 it is therefore evident that, under the conditions employed, 

 only one determination could be made in a day. 



Each morning a new volume of water was used, its freezing- 

 point ascertained, and a more or less concentrated sugar solu- 

 tion prepared from it and the freezing-point determined as 

 described. The precaution was taken to prepare the one-half 

 normal sugar solution from some of the same specimen of 

 water whose freezing-point was determined on the day that 

 this solution was used. 



The Results. 



Grams 

 in litre. 



Normal. 



Lowering 

 found. 



Gram-mol. 

 Lowering. 



3-8875 



0-01136 



0-0251 



2-21 



7-775 



0-0227 



0-0475 



2-09 



15*550 



0-0455 



0-0915 



2-01 



23*325 



0-0682 



0-1333 



1-95 



31-100 



0-0909 



0-1734 



1-91 



These results show by comparison with those obtained 

 when a much colder freezing-mixture was used, that the 

 temperature of this mixture is to be considered in the case of 

 such a substance as cane-sugar. The molecular lowerings 

 here are throughout somewhat lower than the preceding 

 series. To test the measurements a duplicate series was 

 made. 



« * Zeit.f, phys. Chem. xi. p. 532 (Q). 



