]\(pour-Jh'nsitf'i's of some Carbon Cornpoiaids. 507 



tuhiiig- to a ea})illarv tube, dipping into clean dry mercury ; 

 this rubber tube was closed by ii screw clip. The volmne- 

 tube was then placed in a long glass jacket having a boiling- 

 bulb sealed to one side near the lower end ; it contained 

 broniobenzene, and the vapour kept the tube at the tempera- 

 ture of IGO" for a considerable time, during which it was 

 from time to time exhausted by the pumj). After cooling, 

 mercury was allowed to enter through the capillary tube 

 attached to a, until the volume-tube was completely filled. 

 After this treatment no bubbles of air or gas are developed 

 on heating to 130°, the temperature of experiment. The 

 tube w^as then disconnected from the pump ; the rubber 

 stopper with the attached drying-tube removed, and the 

 volume-tube was placed mouth downwards in a trough 

 of mercury. 



The previously weighed bulb containing liquid was then 

 broken at the nick under the mercury, and the two portions 

 of the tube were immediately inserted into the mouth of the 

 volume- tube, into w^hich they rise, and are trapped in the 

 cap at the top. 



On account of the bulb not being completely full of liquid 

 nothing escapes ; on the contrary, as soon as the tube is 

 broken mercury rushes in and fills the capillary portion of 

 the stem, which, as previously mentioned, contains only 

 vapour at very low pressure. 



The volume-tube is then removed from the trough, tlie 

 mouth being closed by the finger, and placed in a nearly 

 vertical position ; the thermometer e is next inserted, and the 

 side tube attached to the manometer. The jacket is slipped 

 over the volume-tube, and after adjusting to verticality with 

 a plumb-line the condenser-tube at the top of the volume- 

 tube is sealed to the gauge-tube, and the pressure under 

 which the chlorobenzene boils is adjusted. 



During the experiment the bulb remains at the top of the 

 volume-tube, along wdth a small globule of mercury; the 

 latter gives off vapour quickly, and the heavy mercury- vapour 

 falls and mixes with the vapour of the liquid ; it is only in 

 this manner that it is practicable to saturate the space w4th 

 mercury-vapour w^ithout protracted delay. 



After the experiment is finished the rubber tube joining a 

 to k is clipped, disconnected, and attached to a flask in which 

 a partial vacuum is made with a Fleuss pump ; the greater 

 part of the mercury is thus withdrawn from the volume-tube. 

 The rubber tube is again clij^ped, disconnected from the flask, 

 and attached to a capillary tube of very fine bore; on opening 



