198 On the Freezing-points of Dilute Solutions. 



introduces no proof for this assertion no one could wonder 

 from the above. But that each one may judge for himself 

 we insert the following passage from a paper in which we refer 

 to the results of other authors, and to which alone Mr. Jones's 

 severe reproach could relate : — 



" It is not without interest to test the earlier values for this 

 source of error through which partly they have been rendered 

 so considerably inaccurate : for instance, for the molecular 

 lowering of the freezing-point (computed from Raoult) for 

 dilute (about 1 per cent.) cane-sugar solutions the following 

 values were found by 



Arrhenius. Raoult. Jones. Loomis. 



2-02 2-07 2-18 181 



but we find, as was mentioned, 1*86 (uncorrected from 1*6 to 

 2*1). Arrhenius used the usual Beckmann apparatus with 

 quite an energetic cooling-mixture : this explains why his 

 value is considerably too large. Raoult gives more experi- 

 mental details, and from these one can conclude that he kept 

 the cooling-bath about 3° below the freezing-point of the 

 solution. This investigator seems to have appreciated the 

 essential importance of the cooling-bath, for he says, ' If the 

 influence of the cooling-bath upon the temperature of the 

 liquid at the moment of freezing is not nought, yet it is 

 indeed the same in the experiments to be compared and 

 vanishes from the differences, so that the lowering of the 

 freezing-point is not influenced by it.' The assumption which 

 Raoult here makes is identical with the supposition that K 

 has the same value for pure water and for solutions, which 

 is certainly not the case with cane-sugar according to our 

 experience. His values must accordingly be considerably too 

 high. Still more erroneous are the values of Jones, who used 

 a cooling-mixture of ice and salt, therefore an exceedingly 

 strong cooler. If Jones had used a single time in the ciise of 

 cane-sugar another cooling- mixture, or even only a freezing- 

 vessel of other dimensions, he would have observed with the 

 great accuracy with which he read the apparent freezing- 

 points the influence of these factors, and would have refrained 

 from publishing his essentially accidental numbers. [Note: — 

 " Since the corrections for Jones's values amount to hun- 

 dredths of a degree, if the accuracy is to be increased to 

 within O'OOOl with the same external temperature and rate 

 of stirring only by using a greater volume of the liquid, in 

 order to reduce K (cf. equations (3) and (7) to its hundredth 

 part, it is necessary to increase the linear dimensions of the 



