52 Dr. Vogel on Mineral Waters. 



An equal portion of ILme water not having been in contact 

 with carbonic acid gas was brought to ebiilUtion in the way 

 just described ; it was precipitated in a much smaller propor- 

 tion, and the precipitate was dissolved in muriatic acid vcithmit 

 any effervescence ; consequently carbonate of lime had been 

 precipitated in the first case, and hydrate of lime in the latter. 



Though both lime water and barytes water absorb carbonic 

 acid speedily, and the carbonates are precipitated very readily 

 in both, but particularly in a solution of barytes, yet lime water 

 and barytic water, when previously mixed with ammonia, are not 

 in the least rendered turbid by a small proportion of cai'bonic 

 acid gas, and the earthy carbonates are wholly precipitated 

 from them by ebullition only. 



Lime water acts in the same manner when poured into 

 a solution of alkaline carbonate of ammonia ; the transpa- 

 rency is slightly clouded, and immediately after restored, and 

 ebullition is required to obtain a precipitate ; but if a greater 

 proportion of lime water be added to the carbonate of ammo- 

 nia, a permanent precipitate is produced. 



These phaenomena naturally suggest the question, whether 

 those carbonates dissolve in ammonia and form salts with dou- 

 ble bases, or from what other cause these carbonates are not 

 readily precipitated from a liquid, which contains no super- 

 abundant acid, but which on the contrary is alkaline. 



Concrete carbonates do not dissolve again in ammonia; how- 

 ever, it does not appear improbable to Dr. V. that a super- 

 abundance of ammonia is an obstacle to their concretion, and 

 consequently that the ammonia at least in the liquid state forms 

 a peculiar salt with those carbonates, whose equilibrium is af- 

 terwards disturbed by the evaporation of a part of the ammonia, 

 which thus occasions a complete decomposition. 



Carbonate of lime obtained by muriate of lime and ammonia, 

 when sufficiently washed, does not retain any ammonia; but 

 carbonate of barytes obtained in the same way, when brought 

 to a red heat, still allbrds some ammoniacal gas. 



If therefore muriate of "barytes or muriate of lime, mixed 

 with ammonia, were employed for detecting carbonic acid, it 

 would be necessai'v to boil these liquids for some time in order 

 to separate the carbonates entii'ely. 



But if it were desired to know the exact proportion of car- 

 bonic acid gas on the spot at a mineral spring where no mer- 

 curial apparatus was to be procured. Dr. V. for the above rea- 

 sons considers as the surest means, to pass the gas through 

 barytic water, and to determine the volume of the carbonic acid 

 gas from the weight of the carbonate of barytes when dried. 



XIII. On 



