CARBONIC ACID. 191 



The so called " soda water," or " mineral water," is 

 prepared by confining water in a strong metallic ves- 

 sel, and forcing into it gaseous carbonic acid, by means 

 of a forcing-pump. The increased quantity which it 

 is thus made to absorb is in precise proportion to the 

 pressure employed. Neither of the above names give 

 a correct notion of the nature of the ef- 

 fervescent drink referred to. It is sim- 

 ply carbonated water, to which soda is 

 sometimes added. 



469. The absorption of carbonic acid 

 by water may be shown, like that of 

 chlorine, by the method illustrated in 

 the figure. It may also be shown by pouring a gill 

 of water into a half-pint vial of carbonic acid, and 

 then shaking it. The palm of the hand being pressed 

 closely upon the mouth of the vial, the flesh will be 

 more or less drawn in, to take the place of the gas ab- 

 sorbed. The vial maybe supported by this attach- 

 ment. 



470. EFFERVESCENT DRINKS. Cham- 



What is said 



of effervescing pagne, sparkling beer, and mead, congress 

 water, and similar drinks, owe their effer- 

 vescent qualities to this gas held in solution. On expo- 

 sure to the air, the gas gradually escapes, and the liquids 

 become insipid to the taste. The air enters and takes 

 its place, expelling sixty or seventy times its own vol- 

 ume of gas. This effect may be hastened by striking, 

 with the hollowed palm of the hand, upon the top of 

 a glass partly filled with one of these liquids ; there- 

 by compressing the air, and forcing it to enter rapidly. 



