Adeney — Dissolved Gases and Fermentative Changes. 555 



at which the measurement for the determination of the oxygen was made. This 

 height may be quickly determined for each experiment by noting the height of 

 mercuiy in the pressure tube, when the mercury in the burette is adjusted at the 

 said line of measurement in vacuo. 



The residual gas, after the absorption of the carbon dioxide and oxygen, may, 

 in some cases, contain hydrogen, and possibly marsh gas. 



When this is the case the following procedure is adopted : — 



After carbon dioxide and oxygen have been absorbed and determined, the 

 remaining gases are driven back into the laboratory flask, and the laboratory 

 vessel and burette are very carefully cleaned. 



To do this the reagents in the laboratory vessel are driven gradually above 

 the rubber collar on the end of the capillary branch tube by lowering the vessel 

 a little from the collar, and carefully raising its reservoir. As the reagents rise 

 above the collar they are absorbed by means of blotting paper. When the vessel 

 has been cleansed by this means as far as possible, it is I'eplaced in position, and 

 about 50 CCS. of dilute suljDhm'ic acid (1 : 3) are introduced into it through 

 the reagent tube. A little of the acid is allowed to rise above the rubber 

 collar to neutralize the potash adherent to it, and the remainder is drawn into 

 the burette. 



The laboratory vessel is then completely detached from the capillary branch 

 tube, and the acid, after having been drawn down nearly to the bottom of the 

 burette, is discharged from it into a beaker. 



The laboratory vessel is next placed in position and filled with tap-water 

 through the reagent tube, and a similar series of operations again cai'ried out as 

 above described, with the view of washing both vessel and burette free from acid ; 

 the washing is repeated two or three times with distilled water. 



When the operation of washing has been completed, the liquid in the laboratory 

 flask is boiled, and the gases drawn from it into the bm'ette and laboratory vessel, 

 with the precaution previously described for their complete expulsion. After 

 their measurement, some pure oxygen is introduced into the laboratory vessel 

 through the reagent tube in a manner exactly similar in principle to that above 

 described for the introduction of liquid reagents. The mixed gases and oxygen 

 are then measured, and exploded under reduced pressure, and the further analysis 

 proceeded with in the ordinary way. 



Since the water surrounding the burette becomes unequally heated during the 

 process of extracting the gases from the laboratory flask, it is necessary to replace 

 it before measuring and analysing the gases. This is readily done by syphoning 

 off the water immediately after the process of exhausting the flask has been 

 completed, and replacing it with some that has been exposed for some time to the 

 temperature of the laboratory. 



TRANS. ROT. BUB. SOC, N.S,, VOI.. V. PAET XI. 4 K 



