90 OIL-FIELD WATERS IN SAN JOAQUIN VALLEY, CAL. 
sumed that a considerable proportion of alkaline earth carbonates 
will be formed and removed by precipitation, leaving the chief con¬ 
stituents of the water alkalies and carbonate. These waters, how¬ 
ever, are less concentrated than sea water, and therefore the amount 
of alkaline earths that can be held in solution in the presence of 
carbonate, if expressed as a percentage, will he much greater. The 
alteration of a meteoric water results essentially in a change from 
primary and secondary salinity to primary and secondary alkalinity, 
the percentage of the last property being only moderate. These 
changes are partly shown by the first three analyses in figure 5, A, 
and the complete transition from normal through modified to altered 
waters of meteoric origin by the analyses in Tables 4, 5, and 6. 
Altered waters of the mixed type are derived by the mixing of 
primary alkaline waters (reversed type) and brines. It has been 
shown above that if all of the sulphate is removed from sea water 
and carbonate substituted the resulting brine will still be charac¬ 
terized by a considerable proportion of secondary salinity, which 
must be chloride salinity. The reaction that ensues when a sodium 
carbonate water is added may be written thus: 
Secondary salinity+Primary alkalinity=Primary salinity-f-Secondary alkalinity 
CaCl 2 + Na 2 C0 3 = 2NaCl + CaC0 3 
The addition of a primary alkaline water to a brine increases the 
alkalies without corresponding increase in strong acids and second¬ 
ary salinity is therefore reduced. Secondary alkalinity may be some¬ 
what increased, as the concentration of the brine is decreased by 
the addition of the more dilute water, but this change is not likely 
to be pronounced. If a sufficient amount of the sodium carbonate 
water is added it is evident that all the secondary salinity will be 
destroyed and that the water will then be characterized by only two 
properties, primary salinity and secondary alkalinity. (See analysis 
46, Table 8, p. 73.) Any further increment of sodium carbonate 
water will then introduce primary alkalinity, which will continue to 
increase as more of the carbonate water is added. The average 
concentration of most of the brines is about 35,000 parts, whereas 
that of most of the primary alkaline (meteoric) waters is only about 
3,000 parts; hence, the concentration of the mixed water will be 
some intermediate figure, depending on the proportions of the mixture. 
If the brine component predominates primary salinity and the con¬ 
centration will be high and primary alkalinity low, but as more and 
more of the meteoric water is added primary alkalinity will increase 
and primaiy salinity and concentration will decrease. (See analyses 
60, Table 10, p. 76, and 72, Table 11, p. 77.) 
The transition from brine to the mixed type is shown in figure 7, 
in which are plotted the reaction properties of the waters from four 
wells along the -east-west line that separates the Midway and Sunset 
