CHAPTER VII. 



GLUCOSE. 

 PRELIMINARY DETERMINATIONS OF OSMOTIC PRESSURE. 



The three series of measurements of the osmotic pressure of glucose, 

 which are to be reported in the present chapter, were each made 

 concurrently with one or another of the eight preliminary series on 

 cane sugar, which have been described in Chapter VI. Their principal 

 purpose, like that of the earlier work upon cane sugar, was the devel- 

 opment of the method. 



It was apprehended that greater difficulty would be experienced in 

 securing solute-proof membranes for glucose than for cane sugar, and 

 such was found to be the case. It was not possible to decide, however, 

 whether this was due to the easier penetration of the membranes by 

 glucose, or to the fact that the membranes in cells containing glucose 

 were (apparently) much more vigorously attacked by penicillium than 

 those in cells containing cane sugar. 



The manipulation and the facilities for the maintenance of tempera- 

 ture were precisely the same for glucose as for the cotemporary work 

 upon cane sugar; and, since these have been fully described in connection 

 with the latter, it will be necessary only to designate the chronological 

 parallelisms of the work upon the two substances. 



Series I.* 



Series I (for glucose) and Series II (for cane sugar) were carried out 

 during the same year and under the same conditions. 



The material employed was the so-called " Traubenzucker Kahlbaum." 

 It was pulverized and freely aerated over calcium chloride by means of 

 a current of dried air, in order to hasten the removal of the odor of 

 alcohol. After this treatment, the material did not sensibly lose in 

 weight when heated to a higher temperature in an air-bath. It melted 

 quite sharply at 146°. Two determinations of carbon and hydrogen 

 gave 40.03 and 40.04 instead of 39.98 per cent for the former, and 6.48 

 and 6.83 instead of 6.71 per cent for the latter. 



The penicillium was not under good control at this time and its 

 attacks upon the membranes were persistent and destructive through- 

 out the whole series. Without doubt the results suffered somewhat, 

 in point of accuracy, on that account. 



* Measurements by H. N. Morse, J. C. W. Frazer and B. F. Lovelace. Am. Chem. Jour., 

 xxxvii, 324. 



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