344 



ON THE PLACE OF FISH IN 



Carbonic 

 acid. 



Test for its 

 presence. 



be obtained, however, by interfering with the flame, for 

 in a flame properly burning it will all be oxidized and 

 pass away as carbonic acid. Indeed, if the Carbon 

 collected on the plate be scraped off and put on to 

 a shovel over the fire, the oxidation will be resumed, 

 and it will all pass away as carbonic acid. 



Carbonic acid is an invisible gas, but there is a very 

 simple way by which its presence can be detected. 

 It readily unites with lime to form the compound 

 carbonate of lime, and is therefore frequently used as 

 a test for the presence of lime in water. The carbonate 

 of lime forms as a fine white powder which gives at 

 first a milky appearance to the water, clearing as 

 the powder settles to the bottom. As the result of 

 the combination of the two is always the same, lime 

 water is a ready test for the presence of carbonic acid. 

 It can be obtained cheaply at a druggist's. The carbonic 

 acid given off by a flame can easily be collected in any 

 jar, which will not crack with heat, by holding it so 

 that the flame is well within its mouth. It will be 

 known when no more will be formed, as the light will 

 then " go out," that is oxidation will cease, because 

 there is no more free Oxygen within the jar. If the 

 jar is then turned over, and a little clear lime water is 

 poured in and well shaken about, so as to absorb the 

 carbonic acid, the milkiness, due to the white powder 

 being formed, will be seen. 



It will probably help to bring home more forcibly 

 some facts that will presently be referred to, if the 

 experiment be repeated with some fat such as would 

 be used for food. It is not much trouble to make 

 a sort of candle of it with some darning worsted as 

 a wick, so that the fat can be oxidized (i.e. burnt, 



