CHEMISTRY — morse;. 21 7 



to find the probable cause of the peculiar conduct mentioned above, or at 

 least to discover a course of procedure in the treatment of the membranes 

 which obviated the difficulty. 



(3) Manometers. — Numerous improvements in the manometric portion of 

 the work were described in a paper which appeared in October, 1908 (Amer- 

 ican Chemical Journal, xl, 325) ; but the obvious necessity of developing this 

 branch of the investigation to the highest possible state of perfection before 

 attempting to settle finally the temperature coefficient of osmotic pressure, 

 led us into a protracted and careful examination of the manometers which 

 are employed in the measurements. In the first place, there was devised and 

 brought into successful working condition an observation chamber for the 

 manometers, which could be maintained automatically for any required 

 length of time, at any desired constant temperature, and in which the instru- 

 ments could, at a constant temperature, be calibrated and compared one with 

 another and with a standard manometer, under varying pressures. The mano- 

 meters were opened and recalibrated by different methods. They were then 

 filled with purified nitrogen, and the volumes of the gas were determined 

 under ten different known pressures which corresponded with the mean 

 pressures of the ten concentrations of solution which we are accustomed to 

 measure. Finally, the manometers were compared, one with another and 

 each with the standard instrument, under the same ten different pressures. 

 The work of the past year in this direction was elaborate and thorough, and 

 consumed over eight months of time. 



(4) The Regulation of Temperature. — The exact regulation of tempera- 

 ture for long periods is of fundamental importance in the measurement of 

 osmotic pressure, and we described, in a paper which appeared in February, 

 1909 (American Chemical Journal, xli, 92), the automatic system developed 

 by us. during the past ten years, for this purpose. Other improvements have 

 since been introduced until, at the present time, the maximum fluctuation in 

 the temperature of the large baths during a series of measurements does not 

 exceed 0.02°, and the difference between the temperature of the solutions 

 and that of the manometers is too small to introduce sensible errors. 



Five series of measurements of the osmotic pressure of cane-sugar solu- 

 tions have been carried out during the year, each series consisting of dupli- 

 cate or triplicate determinations on ten concentrations of solution. 



Two of the five series, one at 25° and the other at 20°, were completed 

 before «ome of the latest and most important improvements in method had 

 been introduced, and they can not, therefore, be considered as having quite 

 equal weight with the last three series of measurements, which were carried 

 out under more favorable conditions. An account of the work at 25° ap- 

 peared in January, 1909 (American Chemical Journal, XLi, i), and of that 

 at 20° in April, 1909 (American Chemical Journal, xu, 257). 



