17 



4. HERMETIC MOIST CHAMBER. 



The hermetic moist chamber for injections under anaerobiosis was made of glasB, 

 the joints being cemented together with balsam (see Figure 12). It consisted of 

 two troughs, one to hold mercury for sealing the chamber and the other to serve 

 as the moist chamber proper. The latter contained a gas inlet and an outlet. 

 Through the axis of the inlet there passed a capillary tube used for delivering 

 the reduced dye into the moist chamber under complete exclusion of oxygen. The 

 chamber was 30 x 40 ram and 15 mm high; and the total volume, including the gas 

 space over the mercury seal, was about 25 oc. Purified nitrogen was passed through 

 at a rate varying from 50 to 250 cc per minute. The chamber was roofed over by a 

 coverslip (40 x 60 mm) and sealed by strips of mica, all heavily coated with 

 vaseline and pressed firmly on the broad contact surfaces. The seal was tested 

 fer tightness and found to withstand a pressure of at least 2 to 3 cm. of water. 

 The diffusion of oxygen through the vaselined seals was of a negligible order, or 

 else it was effectually eliminated by the constant stream of purified nitrogen 

 passing through the chamber,, for drops of reduced indicator often remained un- 

 colored on the coverglass for several hours during an experiment. 



Pi*, a 



Purification of nitrogen. - An essential part of the experimental technic is the 

 particular care to eliminate leakage of atmospheric oxygen into the anaerobic 

 system. Unprotected rubber connections are dangerous because oxygen diffuses 

 through the rubber in quantities sufficient to upset conditions and lead to 

 erroneous conclusions. This point needs emphasis. Cohen, B. , Chambers, R. , and 

 Reznikoff, P., 1928. 



