RICHARDS AND LAMB, — SPRriFIC IIP^AT OF LIQUIDS. GG7 



with a water pump. The pimip was started and the liquid in the spiral 

 kept boiling until most of it h;nl boiled or been ejected over into the 

 filter flask. The pum}) was then disconnected, and the liquid, free 

 from air, was now pressed by the atmosphere back into the spiral. 

 Elnough liquid was always previously placed in the filter fla.'^k, so that 

 at the end no air would go back with the liquid. This process was re- 

 peated several times at each end of the spiral. The bubbles were thus 

 removed with such certainty that the opacity of the metal tube is not, 

 a.s Bradley feareil, a disadvantage. 



The shape of the thermostat was of course governed by the shape 

 and dimensions of the pipette. Further, it had to be provided with a 

 protruding jacket or snout surrounding the lower tips of the pipette, else 

 the temperature of the liquids would be altered in running out. The 

 water in the thermostat was vigorously stirred by means of a small, but 

 rapidly revolving, propeller. This did not have much effect on the water 

 in the snout, and a second smaller propeller was attached to the same 

 shaft and made to fit quite closely mside of a glass tube. From the end 

 of this glass tube a rubber tube extended down to the very tip of the 

 snout. This second propeller acted as a pump, and kept up a vigorous 

 circulation of the water in the snout. 



The hot water was furnished by a large copper thermostat heated by 

 gas. Its temperature was kept constant by means of an ordinary Ost- 

 wald regulator at about 50^, that is, about 16° above that of the hot 

 pipette-thermostat. A regulator is scarcely necessary, as large fluctu- 

 ations in temperature seem to have no effect on the constancy of the 

 hot thermostat. The water, as it left the heater, was filtered through a 

 piece of fine silk cloth. 



As long as the mercury and the glass cut-off were fairly clean, this 

 thermostat proved admirably suited to the purpose. When eciuilibrium 



