Adeney— An Apparatus for Gas Analysis, 8fc. 551 



apparatus for me. About 175 c.c. of air were drawn into the 

 burette through the tube h, the stopcock was closed, and the air 

 was compressed until the level of the mercury in the burette 

 reached the 100 c.c. division. The pressure exerted by the air was 

 then found to be equal to 410 mms. of mercury plus that of the 

 atmosphere, viz. 759*51, that is a total pressure of 1169-51 mms. 

 of mercury. The air was then passed into the laboratory vessel 

 and back again, the mercury being returned to the same level in 

 the burette ; the pressure was read, and found to be exactly the 

 same as before, viz. 116951 mms. The experiment was repeated, 

 and a like result obtained. It was then decided to try a similar 

 experiment with a small volume of air under reduced pressure. 

 About 3 c.c. of air was drawn into the burette, as before, the stop- 

 cock closed, and the volume expanded until the mercury reached 

 the level of the 14 c.c. division line. The pressure of mercury 

 then indicated by the pressure tube was equal to 161 mms. of 

 mercury ; on passing the air int o the laboratory vessel, and back 

 again, and adjusting the mercury to the same level as before, the 

 difference of pressure indicated by the pressure tube was found to 

 be less than O'l mm. It is hence evident that the bubble of gas 

 retained in the laboratory vessel is too small to introduce any 

 appreciable error when the adjustments of the levels of the 

 mercury in the burette and laboratory vessel are made, before 

 making measurements, in the manner above described. 



The following results, taken at random, of analyses of sewage 

 and of air will serve to indicate the degree of accuracy which is 

 ordinarily attainable with the apparatus : — 



(I.) Analyses of the gases resulting from the combustion of 

 the residue obtained by evaporating 50 c.c. of the sample of 

 sewage with metaphosphoric acid to dryness. 



All measurements made at the 14 c.c. division line on the burette. 



Closed pressure tube employed. 



I. II. 



mms. mms. 



Height of mercury in pressure tube (moist), 776-5 786-0 



,, ,, in burette, . . . 35T0 351-0 



Pressure of the gas, 425-5 435-0 



Temperature, 20°C. 20°C. 



