OSMOTIC PRESSURES OF AQUEOUS SOLUTIONS OF CALCIUM FERROCYANIDE. 185 



current. A run of 70 hours resulted in a gain of weight in the 1st vessel of 

 O'OOOS gr. The weight of the 2nd vessel was lost by an accident. 



This experiment was again repeated with three vessels in series, the only change 

 being the use of graphite as a lubricant for the rubber plugs. A run of 70 hours gave 

 a gain in 1st vessel = 0'0045 gr., in 2nd 0'0034 gr., in 3rd O'OOIO gr. 



G- 



Fig. 2. 





Another run of 70 hours resulted in a gain of 0'0032 gr., O'OOl 9 gr., and O'OOOO gr., 

 respectively. 



The rubber plugs were then given \ip and a plain mercury cup joint used, as in 

 fig. 3 (p. 18G). 



A and B are the exit and entry tubes of the vessels, C C are the glass cups, fused to 

 A and B, to contain the mercury. The inverted U-tube D is held in position by a 

 clamp (not shown) supported from the oscillating platform. 



The following tests of this joint were made : 



Three vessels, containing sulphuric acid, were placed in series, and air passed for 

 92 hours; 1st vessel gained 0'0035 gr., 2nd O'OOOS, and 3rd 0'0025 gr. 



It was thought that possibly the cups were not properly cleaned out before 

 weighing, as it was found that the water of the bath had, during the experiment, 

 become charged with rust from the clamps. A repetition of the experiment on a 

 116-hour run (using brass clamps) gave gains of - 0045 gr., 0'0021 gr., and O'OOIG gr. 

 respectively. In both these experiments the temperature of the bath was that of 

 the laboratory. 



VOL. CCIX. A. 



2 B 



