Throughout the construction of the respiration apparatus and its various
parts, it was constantly borne in mind that the slightest leak would be
very disastrous for accurate oxygen determinations. At any point where
there is a pressure greater or less than that of the atmosphere, special
precaution must be taken. At no point in the whole apparatus is it
necessary to be more careful than with the couplings which connect the
various absorber systems with each other and with the valves; for these
couplings are opened and closed once every hour or two and hence are
subject to considerable strain at the different points. If they are not
tight the experiment is a failure so far as the determination of oxygen
is concerned. For the various parts of the absorber system we have
relied upon the original type of couplings used in the earlier
apparatus. A rubber gasket is placed between the male and female part of
the coupling and the closure can be made very tight. In fact, after the
absorbers are coupled in place they are invariably subjected to severe
tests to prove tightness.
For connecting the piping between the calorimeter and the absorption
system we use ordinary one-inch hose-couplings, firmly set up by means
of a wrench and disturbed only when necessary to change from one
calorimeter chamber to another.