1622 
was constantly being replaced by new sea-water, there will have 
formed in a long period a chemical equilibrium between the ions 
Na, Mg and Ca in the sea-water and the atoms Na, Mg and Ca in 
the silicates. 
When this sea-water became displaced by water in which the 
ions Na, Mg and Ca were present in another proportion, namely 
in that of the above-mentioned fresh water, the chemical equili- 
brium was upset and an exchange was bound to take place. 
Whereas, as has been observed, in the normal salt water the 
sodium is very predominant, the calcium predominates strongly in 
the normal fresh water derived from precipitant water. In conse- 
quence of the exchange the proportion of the ions Na, Mg and Ca 
in the penetrated fresh water will agree more with that of sea-water, 
and only when the fresh water has circulated for a certain time, 
the proportion of these ions will, as has been observed, get again 
nearer to that of the normal fresh water. 
By assuming that the solid matters in the soil endeavour to form 
a chemical equilibrium with the cations of the underground water 
it is possible, in connexion with the penetration of the fresh calea- 
reous water to explain the formation of water rich in sodium but 
with a small chlorine content. For in the normal fresh water the 
Ne 
ratio eq. in = about 2.38. If now 
is about 1.38 and the ratio eq. 
7 : : a 
the greater part of Ca is replaced by Na, the ratio eq. CI be- 
comes very great and approaches more and more to the sum of eq. 
‘ 
Na + En — about 4. 
yl Cl 
If such fresh water rich in sodium is evaporated to a small volume, 
the Ca is nearly all precipitated as normal carbonate, also the greater 
part of the Mg. In the solution thus remain principally Na, Cl and 
CO, with a little Mg. 
For that reason such water has been called ““water containing soda” 
or water containing an excess of sodium carbonate. The name 
“alkaline water’ is also applied, presumably because the residue 
when redissolved in water has a strongly alkaline reaction. 
This alkaline water is often met with in places where we may 
expect that the salt water has been displaced latterly by fresh water. 
Consequently it is found there where at a greater depth, the fresh 
water borders on the salt water, but also in the midst of the fresh 
water near beds of loam and clay. 
This fact is apparently in conflict with the above explanation of 
