546 Scientific Proceedings, Royal Dublin Society. 



which is drawn out to a fine point, and the other end is bent at 

 right angles, and has attached to it a piece of stout indiarubber 

 tube about 15 cms. long, and 1 mm. bore. "When the cork is 

 fixed in its place, the fine point of the re-agent tube projects into 

 the interior of the vessel for about 2 cms. A small bunsen 

 screw clamp is also provided with which to close the indiarubber 

 tube when necessary. 



The apparatus and stand should be permanently set on a small 

 table of such a height that the mercury reservoirs may be lowered 

 some 36 inches below the level of the lowest scale mark on the 

 burette. 



The heights of the mercurial columns corresponding to the 

 different divisions of the burette are determined in the ordinary 

 way with the aid of a kathetometer. 



To calibrate the burette, it is filled with water in the following 

 way : — The burette and glass tube g are first filled with mercury 

 by raising the reservoir ; a beaker containing water is then held 

 under the open end of g, and the reservoir lowered until the 

 burette is filled with water down to the lowest division line. The 

 beaker is now replaced by a small tarred flask, and the reservoir 

 slowly raised until the next division on the burette is reached by 

 the mercury ; the water displaced is received into the tarred flask, 

 and weighed ; a similar operation is repeated for each division on 

 the scale of the burette. Finally, the capacity of the tube g is 

 measured. During the process of calibration the wide glass 

 cylinder which surrounds the burette is filled with water in order 

 to maintain the water in the burette at a constant and known 

 temperature. 



During the analysis of a mixture of gases, all measurements 

 are carried on with the level of the mercury in the burette ad- 

 justed to the same division line. The selection of the division 

 line must naturally depend on the volume of the gas to be ana- 

 lysed, and the object of the analysis. 



An arrangement for accurately adjusting the level of the 

 mercury in the burette at the division line selected for making 

 measurements may be made thus : — A piece of white paper 

 having a horizontal black line drawn upon it, is gummed to the 

 stand behind the glass cylinder, and at the same level as the 

 division line, an exact adjustment being made with the aid of a 



