C. Le Neve Foster in the
"Proceedings of the Mining Association and Institute of Cornwall" for
1888. The apparatus used is an ordinary corked 8-ounce medicine bottle.
This is filled with the air to be examined by sucking out its contents
with a piece of rubber-tube. Half-an-ounce of dilute lime-water[121]
(tinted with phenolphthalein) is poured in. If, on corking the bottle
and shaking, the colour is not discharged, the air contains less than
0.25 per cent. of carbon dioxide. "If the colour fades slowly, and does
not finally vanish till after a great deal of shaking, it may be assumed
that the percentage of carbon dioxide does not greatly exceed one
quarter; whereas, if the disappearance is rapid after a very few shakes,
the contrary, of course, is the case." The dilute lime-water is measured
out and carried in ordinary half-ounce phials. This method does not
pretend to great accuracy, but as a method of distinguishing between
good and bad air it is very convenient, and will be found useful.
For determining the actual proportion in the air the following plan is
adopted:--Take a bottle which will hold about 50 ounces, and measure its
capacity; fill the bottle with the air to be examined, pour in 100 c.c.
of lime-water, and shake up for some time; add phenolphthalein, and
titrate the remaining calcium hydrate with standard solution of oxalic
acid.
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