374 . GASOMETRIC-MANOMETRIC METHODS 



A test of the anaerobiosos may be made, as suggested by Boell, 

 Needham, and Rogers (1939), by adding leucomethylene blue into 

 a bottom drop under nitrogen and then sealing the diver. The drop 

 will remain colorless for many hours if the filling has been properly 

 conducted. 



(10) MEASUREMENT 



Saturating the Flotation Medium with Gas. The flotation 

 medium should be saturated with air, unless, in a special case, it is 

 considered necessary to saturate it with another gas. The air satura- 

 tion should be carried out at least 1 hr. before introducing the diver 

 in order to allow time for all of the bubbles to disappear. The aera- 

 tion need not be performed before every experiment unless the 

 experiments are conducted at pressures deviating considerably from 

 the normal. The saturation is carried out by removing the flotation 

 vessel from the thermostat, sealing the mouth of the vessel with 

 the finger (not a stopper, since this would increase the air pressure 

 when inserted) , and shaking until the entire liquid is filled with air 

 bubbles. The vessel is replaced in the thermostat, and at 5 min. in- 

 tervals, the process is repeated twice. 



If the medium is to be saturated with a gas other than air, the 

 gas should be washed first in some of the medium or a salt solution 

 of the same vapor tension and then passed through the medium to 

 be used in a stream of fine bubbles. 



When the ground-glass joint is fitted to the top of the vessel, the 

 latter should be open to the outside through the manifold stopcock 

 and the tap (M), Fig. 114 (page 349). This avoids suddenly com- 

 pressing the air in the flotation vessel, which, if a diver is present, 

 will cause undesirable displacements of neck seals. 



The measurement is conducted by the following procedure: 



1. Connect the air bottle with the outside for a moment through 

 the threeway tap (L, Fig. 114), to equalize the pressure with that of 

 the atmosphere. 



2. Place the filled diver in the flotation vessel by either dropping 

 it in, or, preferably, by lowering it in on the wire loop. Should air 

 bubbles be attached to the diver, remove them with the wire loop or 

 lift the diver out of the medium for a moment. If the mouth seal has 

 been made correctly, an air bubble will not form at the mouth of the 

 diver. 



