154 OSMOTIC PRESSURE OF AQUEOUS SOLUTIONS. 



taken views regarding cane-sugar Series I and II were held — the views, 

 namely, (1) that, not having found much invert sugar in Series I by 

 the method of Fehling, the solutions had maintained their concentra- 

 tion; and (2) that, having found considerable loss in rotation in Series 

 II, it was due to inversion caused by penicillium. The early errors of 

 interpretation regarding cane-sugar Series I and II have been corrected 

 in the preceding chapter; but, up to the present time, no good reason 

 has appeared for questioning the general correctness of the results of 

 glucose Series I as they are presented in Table 40. 



Series II.* 



Glucose Series II and cane-sugar Series III were carried out at 

 about the same time and under identical conditions. It was sought 

 in both to maintain a temperature as close as possible to 0°. The 

 means which were employed for this purpose have been described in 

 connection with the account which was given of the work in cane sugar 

 Series III. 



The material used was Traubenzucker Kahlbaum, but in the begin- 

 ning it was distinctly less pure than that employed in Series I. After 

 aerating the pulverized substance and allowing it to stand in an 

 exhausted desiccator until it gave no reaction for alcohol, it was 

 found to have a somewhat uncertain melting-point of 143°. Four 

 determinations of carbon and hydrogen gave: for the former, 40.28, 

 40.26, 40.35, and 40.35 instead of 39.98 per cent; and for the latter, 

 6.60, 6.66, 6.62, and 6.69 instead of 6.71 per cent. A solution, con- 

 taining 32.65 grams of the glucose in 100 cubic centimeters at 17.5°, 

 gave a rotation of 101.45 instead of 100 saccharimetric degrees. Before 

 using the material for the determination of osmotic pressure, it was four 

 times recrystallized by precipitation from aqueous solution by alcohol. 

 Thus purified, its melting-point was found to be 145° to 146° instead of 

 146°, and the standard solution gave a rotation of 100.5 saccharimetric 

 degrees. Two analyses gave: for carbon, 40.09 and 39.96 instead of 39.98 

 per cent; and for hydrogen, 6.64 and 6.77 instead of 6.71 per cent. 



The sum of all the fluctuations in bath temperature was 1.47° and 

 the mean was 0.07°. In the parallel cane-sugar series (III) the sum 

 was 2.81°, and the mean was 0.10°. 



The sum of the rotation of all the solutions of glucose Series II was 

 552.90°. The sum of all the losses in rotation was 5.84°, or 1 .06 per cent. 

 In the companion cane-sugar series, the percentage loss in rotation was 

 1.73 per cent. The dilution in the glucose series was, therefore, less by 

 0.67 per cent than in that of cane sugar. 



Except in the case of the 0.1 normal solution, the ratios of osmotic 

 to gas pressure are quite uniform. In this respect glucose Series II, 



♦Measurements by H. N. Morse, J. C. W. Frazer, and F. M. Rogers. Am. Chem. Jour., xxxvii, 558. 



