84 University Geological Survey of Kansas. 
lent quantity of sodium sulfate and magnesium chlorid, and it 
would be impossible for any one to detect the least difference 
between the two solutions. If the solution is more concen- 
trated so that the dissociation is not complete, there will be 
present the four ions—sodium, magnesium, chlorin, and sul- 
fate, together with the four possible salts—sodium chlorid, 
sodium sulfate, magnesium chlorid, magnesium sulfate. Fur- 
ther, two of such solutions will be absolutely identical, no 
matter which pair of salts be dissolved. Under these circum-. 
stances, it would be obviously incorrect to report the substances 
as present either as sodium chlorid and magnesium sulfate, or 
as sodium sulfate and magnesium chlorid. The only rational 
way is to report them as ions, and this is the method that has 
been given prominence in this work, although the other meth- 
ods have been followed also for comparison. 
Therapeutic Properties Rest Largely in the Ions.—The therapeutic 
propeties of a mineral water are the sum of the properties of 
the ions, together with those of the undissociated portions of 
the salts present. Most mineral waters are so dilute that the 
undissociated portion of the salt may be neglected and the at- 
tention directed merely to the ions. The therapeutic properties 
of the various ions will be discussed in another portion of this 
work. 
Occurrence of Ions in Mineral Waters.—It is of interest to no- 
tice that the following ions which are required by animals for 
their growth and nutrition are all present in mineral waters, 
namely; Na, Cl, CO;,\Ca, 1) Me, 1 Ke, BO, and) SO,5))) Min- 
eral salts are also carried by water to the rootlets of plants, and 
the following ions which are necessary to their growth are pres- 
ent in waters: K, Mg, PO,, CO;, with Ca, in most cases, and 
Mn often; NO, and SQ, are useful as nutrients. 
