CHEMISTRY — MORSE. 



191 



How they do hold for the proportion /* : /\ : : A : Aj (and consequently for 

 all other proper methods of comparison) is shown in table 4. Exact agree- 

 ment between the calculated and experimental values is not to be expected, 

 owing to differences of temperature, and the divergences between them 

 should increase with the concentration. 



Tabi^ 4. 



The excess of osmotic over gas pressure in the vicinity of 0°, while the 

 two were found to be in substantial agreement in the neighborhood of 20°, 

 made it desirable to determine the pressures of both cane-sugar and glucose 

 solutions at several intermediate temperatures, in order to ascertain just 

 where, and at what rate or rates, the divergences observed at low tempera- 

 tures disappear. The intervals selected for this purpose are 5,° 10°, and 15°. 



The work upon cane-sugar solutions at 5° has been completed, and was 

 described in the fourth paper mentioned at the beginning of this report. A 

 summary of the results is given in table 5 on p. 192. 



There is very little evidence to be discovered in the pressures exerted by 

 cane-sugar in solution at 0°, at 5°, and in the vicinity of 20°, of any con- 

 siderable temperature coefficient for osmotic pressure such as that for gases. 

 It would, however, be premature to conclude from this that osmotic pressure, 

 even in the case of cane-sugar, does not obey the law of Gay-Lussac; since, 

 as the author has pointed out elsewhere, it is still possible that the causes 

 which produce abnormal pressures at 0° and similarly abnormal depressions 

 of the freezing-points, disappear gradually with rising temperature, and at a 

 rate which efifectually masks the temperature coefiicient of the osmotic press- 

 ure. It is to be anticipated that much clearer evidence upon this important 

 question will be secured by investigating the osmotic pressure of substances 

 the molecular depressions of whose freezing-points are more nearly equal to 

 the calculated value 1.85 than are those either of cane-sugar or of glucose. 



Drs. J. C. W. Frazer, B. F. Lovelace, W. W. Holland, F. M. Rogers, and 

 P. B. Dunbar have cooperated with the author in the work here reported. 



13— YB 



