Page:Life in Motion.djvu/143

Rh 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

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