248 BACTERIOLOGY. 



Mercury fills the capillary and covers the bottom of the 

 cylinder to a depth of about 1.5 cm. 



The filling 1 of the regulator is not difficult. For this purpose 

 parts B and C are removed, and the end of A, and one of the side 

 arms (a") is stoppered air- tight. The other arm, or gas inflow tube 

 (a 7 ), is connected with a Chapman aspirator. The rubber tubing, 

 leading to the aspirator, should be provided with a clamp or stop- 

 cock. The adjusting screw D, is then removed, and replaced by a 

 short rubber tube provided with a clamp. The rubber tube connects 

 with a short narrow glass tube, which dips into a beaker of absolute 

 alcohol. 



The pump is now set into action. The clamp on the regulating 

 arm D is slightly opened, till the alcohol begins to pass into the 

 tube, after which it is closed. When the air has been evacuated, as 

 much as possible, the clamp on the tubing that leads to the pump is 

 closed, while that on regulating arm is slowly opened. The alcohol 

 rapidly fills the cylinder. If the evacuation is incomplete, the regu- 

 lator should be inverted, and the air again exhausted, after which 

 alcohol can be admitted as before. A few bubbles of air that may 

 persist can be disregarded, inasmuch as they will be absorbed by the 

 alcohol. 



The next step is to introduce the necessary amount of mercury. 

 For this purpose, the alcohol bulb of the regulator is immersed in a 

 water-bath which has been heated to about 70. The alcohol expands 

 and fills the lower portion of A. When A has been nearly half filled 

 with the expanded alcohol, mercury is then added, and the apparatus 

 is allowed to cool. Additional mercury is added, if need be, to pre- 

 vent the entrance of air into the cylinder. The regulating arm is 

 likewise filled -with mercury, and the screw inserted about one- 

 half. 



At ordinary room temperature the mercury in the capillary 

 tube should not be higher than the regulating arm. The ground sur- 

 faces of the regulator should be lubricated very slightly with vaselin, 

 or better with a mixture of bees-wax and olive oil (1 : 4). The inflow 

 tube a' is then connected with a gas-pressure regulator, or with the 

 gas-supply direct. The out-flow tube a" is connected with a micro- 

 burner. A suitable cork, or rubber stopper, is slipped over the tube 

 of the regulator, which is then placed in the thermostat, so that the 

 bulb is immersed in the water. The adjusting screw D is turned out- 

 ward, if necessary, so as to allow the gas to escape from /. The gas 

 is turned on and lighted. As the temperature rises the alcohol ex- 



