134 



OSMOTIC PRESSURE OF AQUEOUS SOLUTIONS. 



regulation. This is done in Table 23, from which it appears that the 

 mean variation in bath temperature in Series IV was more than double 

 that in Series II, as if the means of bath control had decreased, instead 

 of increasing in efficiency. It is easy to show, however, that the condi- 

 tions to be met in the case of Series IV were more difficult than in that 

 of Series II, and that, on this account, the comparison is less unfavorable 

 to the former than it appears to be. Nevertheless, it was considered 

 necessary to revise radically the system of bath regulation before 

 beginning the next series. 



If Series III and IV are compared with respect to the upward dis- 

 placements of the manometers, no evidence of progress is to be detected. 

 It will be seen in Table 24 that the mean displacements were about 

 equal in the two series, which signifies that little or no progress had 

 been made in the direction of fixing the capacity of the cells. 



Table 24. — Cane sugar, Series III and IV. Upward displacements of the manometers (mm.) . 



If, on the other hand, as in Table 25, Series III and IV are compared 

 with respect to loss in rotation, which is the measure of the total 

 dilution which the solutions suffered while in the cells, some improve- 

 ment is apparent. The relatively smaller loss in Series IV was due 

 to improvements in manipulation at the time of closing and opening 

 the cells, particularly during the latter period. 



The sum of the rotations of all the 20 solutions used in Series IV was 

 1249.00°. The loss in rotation was 17.55°, or 1 .41 per cent. The loss in 

 rotation in Series III was 1.73 per cent. Expressed in terms of osmotic 

 pressure, the dilution in Series IV was equivalent to 4.3 atmospheres, 

 and that in Series III to 6.74 atmospheres. 



Table 26 gives the results of Series IV as corrected for dilution, that 

 is, for the observed losses in rotation. It stands in the same relation 

 to Series IV as Table 17 to Series II, and Table 21 to Series III. On 

 the whole, the corrected osmotic pressures of Series IV are probably 

 a little more trustworthy than those of Series III. 



