CAPILLARY RESPIROMETRY 



325 



Brodie fluid is placed in the manometer and water is used in the 

 compensation vessel. A layer of water is also used to cover the 

 mercury in 2. 



The chamber {3) is attached, while both stopcocks are open to the 

 air. At the start of an experiment the stopcocks are set as shown in 



Fig. 99. Volumetric respirometer, 



sensitive to about 0.3 yX. per hour. 



From Scholander (1942a) 



Fig. 100. Volumetric respirometer, 



sensitive to about 0.01 fi\. per hour. 



From Scholander (1942a) 



the figure ; during the experiment the micrometer is used to keep the 

 menisci level in the manometer tube by replacing the oxygen as it 

 is consumed. In order to prevent contamination of the oxygen in 2, 

 the stopcock attached to the oxygen storage vessel is kept closed 

 except when the micrometer adjustment is made. 



Respirometer Sensitive to 0.01 Microliter per Hour. This 

 apparatus (Fig. 100) consists of a micrometer whose spindle has 

 been replaced by a Vie in. diameter drill rod which passes through 

 a fiber washer with an air-tight fit into the glass tube {2) . The glass 

 part is held in the micrometer frame. Oxygen is stored at 3\ the 

 respiratory chamber fits on the side arm at 4; the indicator drop 

 is at 5, and the compensating chamber at 6. The capillary bore is 

 about 0.25 mm. The micrometer is screwed to a heavy brass foot as 

 illustrated. 



The apparatus is first filled with mercury and carefully freed from 

 air bubbles. The reservoir [3) is filled with oxygen after a little 

 water is drawn in to cover the mercury. The respiration chamber is 

 then connected; it contains a loop of platinum wire to hold the 

 sample in a drop of medium while the carbon dioxide absorbent is 



