230 
CHEMISTRY: D. D. VAN SLYKE Proc. N. A. S. 
pipette is allowed to fall to the mark indicating A cc., as shown in the 
figure. Cock c is closed, and the pipette is shaken for the time required 
to establish equilibrium of the gases between the solution and the free 
space above it. One to two minutes 
usually suffice. Mercury is then read- 
mitted at cock c until the gas volume in 
the pipette is reduced to a cc. Cock c 
is closed and the height of the mercury 
column in the manometer is read (m mm.) . 
The zero point is then determined after 
expelling the gases from the apparatus, 
or after absorbing one or more of them 
by introduction of small, measured vol- 
umes of gas-free absorbent solutions (KOH 
for C0 2 , pyrogallol for 0 2 ) through the 
upper cock under slight negative pressure. 
After the gas has been removed the 
pressure is lowered until the free space 
above the solution is again a cc, and the 
zero point for the determination is read 
on the manometer (n mm.). 
The volume, V, of gas reduced to 0* 
tion analyzed is calculated as: 
_ m — n f 273 
V " a 760 \ T A 
T = absolute temperature, 5 = volume of water solution in the apparatus, 
a = solubility coefficient of the gas in the solution (the cc. of gas, reduced to 
0°, 760 mm., dissolved by 1 cc. of solution in equilibrium with the gas at 
760 mm. tension). 
760 mm., contained in the solu- 
- S ) 
The term 
St 
which corrects for the portion of gas remaining in 
A -S' 
solution when equilibrium is reached, may be negligible for the less soluble 
gases, such as oxygen and nitrogen, but not for C0 2 . The term is derived 
as follows. If Vs = volume of gas (measured at 0°, 760 mm.) held in 
solution by the 5 cc. of solution, and p = partial pressure of the gas 
P_ 
760 
a 
V s = SXaX^ 
p = (m — n) X 
V* = a 
m 
50 
X 
-5 
Sa 
760 " A -S 
In case % cc. of absorbent solutions are introduced, a correction to n is 
necessary. It is ascertained by determining m for 5 and for 5 + #cc. of water, 
respectively, the dissolved gases being removed by expulsion. 
