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RESPIRATION
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vacuum, it very quickly dies. The best test for carbonic acid gas is lime-water, which becomes turbid when the gas is led through it or shaken up with it. The chemists have given me this jar of carbonic acid, and you see
Fig. 60.—Breathing into lime-water. Faraday's method as shown in the Chemistry of a Candle.
when I shake up some of this clear lime-water with it, how white and milky it becomes. We can readily, by this test, show you that carbonic acid is produced by breathing, and it is interesting at a Christmas lecture at this Institution to employ the simple method used thirty years ago by Faraday in his celebrated course on the chemistry of a candle. I have two bottles, one containing lime-water and
