360 CARNEGIE INSTITUTION OF WASHINGTON. 



suspended its operations permanently about two years ago. We had 

 at the time an accumulated supply of cells which was sufficient only to 

 carry on the work through a part of the following year. The baking 

 and glazing of the cells was inmiediately transferred to the Bennett 

 Pottery; but it was necessary to repeat, in the new location, the 

 elaborate series of experiments previously made at the Chesapeake 

 Pottery. This work has been under the direction of Dr. Holland. It is 

 by no means finished, but he is already producing usable cells. 



The present problem, which is being worked out with good promise 

 of success at the pottery, is the production of cells so active that the 

 osmotic pressure of cane-sugar solutions in them will reach equilibrium 

 before the auto-inversion of the sugar, which occurs above 60°, reaches 

 a sensible magnitude. A few fairly successful measurements of pres- 

 sure at 70° have already been accompHshed in cells of recent make. 



One important development of the past year has been the construc- 

 tion of a cell for the measurement of very high pressures. It has 

 already been successfully employed for the determination of pressures 

 exceeding 125 atmospheres. 



The osmotic pressiu-e of mannite is of especial interest because the 

 freezing-points of its solutions — unlike those of solutions of glucose 

 and cane-sugar — are normal. In the author's report to the Carnegie 

 Institution, previously cited, it was shown that, between 10° and 40°, 

 the osmotic pressure of mannite solutions is also normal, i. e., that within 

 this temperature-interval it conforms to the gas laws. Only a few 

 measurements of the osmotic pressure of mannite solutions have been 

 made during the past year, and all of these were, as before, within the 

 temperature-limits, 10° to 40°. They were made with a view to the 

 introduction of the interferometer as a means of ascertaining concentra- 

 tion, rather than to secure additional osmotic data. Measurements 

 of pressure below 10° and above 40° have not yet been attempted. 



A considerable number of measurements of the osmotic pressure of 

 levulose at 30° have been made during the past year. In view of the 

 general similarity of conduct on the part of the two substances, it was 

 to be presumed that levulose would be found to exhibit the same 

 osmotic pecuHarities that had been observed in the case of glucose — 

 in other words, that the osmotic pressure of levulose solutions at low 

 temperatures would be found to be seemingly greater than is required 

 by the gas laws; and that the ratio of osmotic to gas pressure at low 

 temperatures would decline to unity at some higher temperature and 

 thereafter remain constant. The temperature at which this ratio 

 became unity for all solutions of glucose was 30°. This temperature 

 was therefore selected for beginning the work upon levulose. 



The costly material for this investigation was provided by Dr. Hud- 

 son, of Washington. It was nearly pure when it came into our hands, 

 and required but little further treatment to render it entirely suitable 

 for our purposes. 



