CHAPTER XIII. 
The Carbonate Group. 
Carbonated waters are perhaps the most numerous of any 
class. ‘These include some very heavily charged with mineral 
matter which has been dissolved from the rocks or soil by the 
carbon dioxid dissolved in the water, and others that contain 
only small quantities of the bicarbonates, as they are called. 
Most of the ordinary spring waters which have a local reputa- 
tion for great therapeutic virtues are of this class; those hav- 
ing an excess of sodium carbonate are also included in this 
group. These are called by many authors the ‘‘alkaline’’ class, 
because they include the alkaline carbonates, potassium, so- 
dium, and lithium, as well as carbonates of the alkaline earths, 
calcium, magnesium, and strontium. These waters usually 
contain an excess of carbon-dioxid (carbonic-acid) gas, more 
than enough to keep the bases in solution. Lime and magne- 
sia, it should be said, are dissolved by water surcharged with 
this gas, in accordance with the well-known reaction : 
CaCO3+ H2O-+CO2 = CaHz (COs)>. 
When a water of this composition evaporates spontaneously, 
as in the roof of a cave, or when it is heated, the water and 
carbon dioxid are expelled, and the calcium carbonate is pre- 
cipitated or separates out in accordance with the reaction : 
CaH»2(COs3)2=CaCO3+ H2O+COs2. 
This accounts for the formation of stalactites and many simi- 
lar deposits. 
These waters usually have an alkaline or neutral reaction. 
If sodium carbonate is present, the reaction is strongly alkaline, 
since carbonic acid is a very weak acid. 
The amount of carbon-dioxid gas dissolved in the Kansas 
waters is small; in fact, there are none of this class that corre- 
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