190 METALLOIDS. 



case, the carbon of the candle is converted into car- 

 bonic acid, by the oxygen of the air. But neither 

 of these methods give the unmixed gas, and that which 

 follows is therefore to be preferred. 



465. ANOTHER METHOD. Pour a tea- 



Give the sec- . . 



ond method of spoonful of muriatic acid into a large- 

 prfpanng it, mou thed half-pint vial, and then 

 ad i bits of marble, chalk, or carbonate of 

 soda, until effervescence ceases. The vial 

 will then be filled with carbonic acid. 



Explain the 466. EXPLANATION. Chalk 



above process. an( j mar ble are both carbonate of lime. 

 As soon as they are dropped into muriatic acid, this 

 stronger acid combines with the lime, and retains it, 

 setting the carbonic acid at liberty in the form of a gas. 

 The gas as it accumulates, expels the air from the vial, 

 and completely fills it. It is obvious that in this method 

 we do not make carbonic acid, but use that which na- 

 ture has already made for us, and imprisoned in the 

 marble. 



467. For most of the experiments that 



Describe ano- 

 ther method of follow, the second simple method of col- 

 preparation. \ ec i{ on j s sufficient, and the gas need not 

 be transferred to another vessel. When 

 it is desired to obtain it separate from the 

 materials from which it is produced, the 

 apparatus represented in the figure may 

 be employed. 



468. CARBONATED WATERS. 



How are car- 



bonatcd waters Water absorbs its own volume of carbonic 

 made l acid, and thereby acquires an acid taste. 



