It is very interestlng to point out that much D.O. has been detected in
the waste from a paper pulp mill only by the polarographic method, or, little
D.O. has been found by the other methods.
When the concentration of organic matter is very high, polarographie
method would also be interfered with by alteration of the drop-time of mercury
and of the diffusion coeflicient of D.O., caused by the viscosity change, and
by compounds which are also reduced at the electrode. However, since the
diffusion current is decreased to a very }ow va}ue by bubbling hydrogen or
nigrogen gas through the waste sample, and since it is re-increascd by re-aeration,
it may be reasonable to assume that much D.O, has been present in that
waste.