As the water-vapor is absorbed by the sulphuric acid, there is a slight
increase in volume of the acid. This naturally results in the diminution
of the apparent volume of air and likewise again affects the amount of
oxygen admitted to produce constant apparent volume at the end of each
experimental period. The amount of increase which thus takes place for
each experimental period is very small. It has been found that an
increase in weight of 25 grams of water-vapor results in an increase in
volume of the acid of some 15 cubic centimeters. Formerly this
correction was made, but it is now deemed unnecessary and unwise to
introduce a refinement that is hardly justified in other parts of the
apparatus. Similarly, there is theoretically at least an increase in
volume of the potash-lime by reason of the absorption of the carbon
dioxide. This was formerly taken into consideration, but the correction
is no longer applied.