CHEMISTRY — MORSE. 



217 



To test this apparent agreement — or, rather, to ascertain beyond a reason- 

 able doubt the temperature coefficient of osmotic pressure — very elaborate 

 arrangements were made to meet and minimize the remaining known defects 

 of the method. The improvements made concerned every phase of the work 

 and in many cases were of a fundamental character. The cells were improved 

 in a number of important particulars. The automatic system of temperature 

 regulation was advantageously modified. The older baths were reconstructed 

 in order to introduce the numerous improvements which long experience 

 with them had shown to be necessary or desirable. Three new baths were 

 built, which made it practicable to deposit the membranes — and to maintain 

 the cells at all times when out of use — at the temperatures at which measure- 

 ments were to be made. Another bath was constructed for measuring press- 

 ure at high temperatures. The largest single source of error in the work at 

 present appears to be the manometers ; accordingly the facilities for the cali- 

 bration and verification of these instruments were increased and greatly im- 

 proved. The above will serve to indicate the thoroughgoing nature of the 

 preparation for the solution of the problem in hand. The essential details 

 will be given in a series of papers about to appear in the American Chemical 

 Journal. 



The results of the actual measurements made under the improved condi- 

 tions are given below in tabular form, except in so far as they have not yet 

 been verified by duplicate determinations. At all points where verification 

 is still lacking the spaces have been left vacant. The table gives the pressures 

 obtained and the ratios of these to the calculated gas-pressure of the material 

 in solution. It is to be noted that all solutions employed in this work are 

 made by dissolving the appropriate weight of material in 1000 grams of 

 water. Comparing the ratios of osmotic to gas pressure, it will be seen that 

 between o° and 25 ° they are very constant for any given concentration. 



The Osmotic Pressure of Cane-sugar Solutions. 



The relation of osmotic pressure to temperature is established in the field 

 covered by the work with much greater certainty than the relation of press- 

 ure to concentration, the reason being that the undeterminable and unknown 

 errors of the manometers are of much less importance in the former than the 

 latter case. The results given in the table have not hitherto been published. 



