ltimate result of which is that at the final
filling with oxygen at the end of the period less is used than would be
the case had there been no change in the barometer. In other words, for
each liter expansion of air inside of the system, there is 1 liter less
oxygen required to bring the apparent volume the same at the end of the
period. Similarly, if there is an increase in temperature of the air,
there is expansion, and a smaller amount of oxygen is required than
would be the case had there been no change; and conversely, if the
barometer rises or the temperature falls, more oxygen would be supplied
than is needed for consumption. It is thus seen that the temperature and
barometer changes affect the quantity of oxygen admitted to the chamber.

INFLUENCE OF FLUCTUATIONS IN THE AMOUNTS OF CARBON DIOXIDE AND
WATER-VAPOR UPON RESIDUAL OXYGEN.

Any variations in the residual amount of carbon dioxide or water-vapor
likewise affect the oxygen. Thus, if there is an increase of 1 gram in
the amount of residual carbon dioxide, this corresponds to 0.51 liter,
and consequently an equal volume of oxygen is not admitted to the
chamber during the period, since its place has been taken by the
increased volume of carbon dioxide. A similar reasoning will show that
increase in the water-vapor content will have a similar effect, for each
gram of water-vapor corresponds to 1.25 liters and therefore influences
markedly the introduction of oxygen. All four of the factors, therefore
(barometric pressure, temperature, residual carbon dioxide, and residual
water-vapor), affect noticeably the oxygen determination.

CONTROL OF RESIDUAL ANALYSES.

Of the three factors to be determined in the residual air, the oxygen
(which is most important from the standpoint of the relative weight to
be placed upon the analysis) unfortunately can not be directly
determined without great difficulty. Furthermore, any errors in the
analysis may be very greatly multiplied by the known errors involved in
the determination of the true volume of the air in the chamber as a
result of the difficulties in obtaining the average temperature of the
air. Believing that the method of analysis as outlined above should be
controlled as far as possible by other independent methods, we were able
to compare the carbon dioxide as determined by the soda-lime method with
that obtained by the extremely accurate method used by Sonden and
Pettersson. An apparatus for the determi