96 BURTON EDWARD LIVINGSTON 



Of course the tube may be connected with the outlet of a 

 burette at a lower level, so that accurate readings may be made 

 directly. In such a case it is advisable to cover the open end of 

 the burette with a suitable cap. 



The bottle is first filled with distilled water. The cup is then 

 filled to overflowing and the rubber stopper is firmly set in 

 place. Then the cup is held downward and the tube is filled with 

 water by pouring from the bottle, after which tube and cup are 

 quickly inverted and the latter is thrust into the bottle, avoid- 

 ing any entrance of air into the open end of the tube. The cork 

 stopper is then firmly placed. It is desirable to allow from 12 

 to 24 hours to elapse before beginning the taking of readings, so 

 that the water films of the cup may come into equilibrium. 

 Where long periods elapse between readings (as of several days) 

 the latter precaution may be omitted, with the introduction of 

 but a comparatively slight error. 



At the beginning of operation the cork stopper is loosened 

 from the bottle, it and the tube are lifted high enough so that 

 the lower surface of the cork is free from the bottle neck, and 

 moved laterally as far as the tube will allow. The tube and cork 

 are now lowered until the lower face of the latter rests upon the 

 top of the bottle, leaving the bottle mouth open sufficiently, 

 alongside the tube, to allow the pouring in of water. The bottle 

 is now filled to the zero mark and the cork firmly replaced. At 

 the end of the period of operation this method of filling the 

 reservoir is again used, the water required being measured from 

 graduate or burette. The amount of water thus required is 

 the loss which has occurred for the period. The manipulation 

 of the cork and tube (with the cup above), as just described, 

 insures that at every filling the same amount of water in the 

 reservoir will be displaced by the tube. When the cork is re- 

 placed the water level rises above the zero mark, but the next 

 filling will be made with the cork and tube in the same position, 

 so that there is no error thus involved. If, when the cork is 

 forced into position, the cup becomes visibly wet on the out- 

 side, this means that the groove in the cork is stopped and re- 

 quires enlarging. In pouring water into the bottle, care should 



