CLASSIFICATION OF THE OIL-FIELD WATERS. 
47 
Silica. —Silicon is nearly always present as the colloidal oxide 
(silica) and may therefore be disregarded in a study of the reactive 
properties of the water. In primary alkaline waters it may enter 
the solution as silicate, hut probably soon breaks down into the 
colloidal form (Si0 2 ). It varies greatly in amount in the oil-field 
waters, hut averages higher in primary alkaline waters than in brine. 
Other constituents. —Several mineral constituents in addition to 
those already mentioned are probably present in the oil-field waters. 
Nitrate has been sought in 27 of the samples here discussed and 
has been found in only 5, of which 4 are surface waters. A small 
quantity of boron was found in the one sample tested for it. Bro¬ 
mine and iodine have been detected in some of the oil-field brines, 
and the iodine was determined quantitatively in one sample. (See 
analysis 58, Table 9, p. 74.) Iodine in unusually large amounts 
in several samples of brine from the Midway and Sunset fields was 
also reported many years ago by Watts. 1 
Total mineral solids. —The total mineral solids present in a given 
quantity of water, or the concentration of the solution, varies widely 
in the different oil-field waters. In the surface water and shallow 
ground water of the Kern River field the content of dissolved mineral 
matter is lowest and is generally less than 200 parts per million. 
All the shallower waters examined in the fields of the west side of 
the valley contain more than 300 parts, and most of them contain 
between 1,000 and 4,000 parts. The concentration in general in¬ 
creases with depth; most of the deeper waters of the Kern River 
field contain between 1,500 and 4,000 parts, and those of the fields 
on the west side of the valley between 8,000 and 40,000 parts. 
Although the concentration of the various types of water is fairly 
regular, individual samples may show considerable variation. 
In the tables of analyses given below the concentration is repre¬ 
sented simply by the totals of the constituents reported except 
when bicarbonate is shown. Bicarbonate is unstable and tends to 
break down into carbonate when the solution is evaporated to dry¬ 
ness; hence, in accordance with convention, the bicarbonate radicle 
is not given its full value in the total but appears as carbonate. 
Organic and volatile matter. —The figure given in most industrial 
analyses under the heading "organic and volatile” represents the 
loss in weight when the solid matter obtained on evaporation is 
heated to redness. It consists chiefly of carbon dioxide and whatever 
organic or hydrocarbon matter was present in the water. Many of 
the primary alkaline waters that have been closely associated with 
the oil contain dissolved organic matter in the form of petroleum 
acids, which would be included in this determination. However, most 
i Watts, W. L., The gas and petroleum yielding formations of the Central Valley of California: California 
State Min. Bur. Bull. 3, pp. 90-91, 1874. 
