Page 196 - Geochemistry of Oil Field Waters

FATTY ACIDS 183

size molecules, with the smallest molecules being practically nitrogen-free.
This is attributed to the fact that the link involving nitrogen is more
susceptible to oxidation than the rest of the molecule. Amino acids can be
released from humic acid by acid hydrolysis, alkaline hydrolysis, and reduc-
tion with sodium amalgam (Piper and Posner, 1968).
A widely used procedure for concentrating and recovering trace organics is
the carbon-adsorption method developed by Braus et al. (1951). A modifi-
cation of this method by Robinson et al. (1967) allowed recovery of
organics using three activated carbon filters in series, with the final two
receiving acidified water.
Krause (1962) investigated the decomposition of organic matter in natural
waters and found that immediately after the death of an organism that
amino acids and keto acids appeared in the water. After 24 hours of aerobic
decomposition, a qualitative and quantitative maximum was reached by both
groups, and the amino acids present were alanine, aspartic, glutamic, glycine,
leucine, lysine, methionine, phenylalanine, serine, tyrosine, and raline; and
the keto acids present were pyruvic, oc-ketoglutaric, oxaloacetic, and
glyoxylic. After 10 days, the only acids that remained of the amino group
were glutamic, glycine, lysine, and serine; and of the keto group, pyruvic and
oc-ketoglutaric.
Litchfield and Prescott (1970) analyzed sea water, and pond water, and
spent algal media and found aspartic acid in all of the samples. Other amino
acids frequently found were serine, glycine, alanine, and arginine. Techni-
ques employed in the analysis were dansylation, extraction, and thin-layer
chromatography .

Fatty acids

Ralston and Hoerr (1942) determined the solubilities of the normal
saturated fatty acids from caproic to stearic acid, whose number of carbon
atoms ranges from 6 to 18 in water, ethanol, acetone, 2-butanone, benzene,
and glacial acetic acid from 0' to about 60'C. In general, the solubilities
increased with increasing temperature.
Free fatty acids and hydroxyl ions form when soaps hydrolyze. The rate
and percentage of hydrolysis is pH dependent, generally the potassium soaps
are more hydrolyzed than the corresponding sodium soaps, and free fatty
acid never separates as such from pure soap solutions unless reacted with an
excess of acid such as carbon dioxide (McBain et al., 1948).
Quantitative recovery of organic constituents from saline waters without
alteration is difficult. Temperature and pressure changes, bacterial actions,
adsorption, and the high inorganic/organic constituents ratio in most
petroleum-associated waters are some reasons why quantitative recovery is
difficult. Some of these factors apply also to sea waters, and Jeffery and
Hood (1958) evaluated five methods which proved effective for isolation
of portions of the soluble organic compounds in sea water. They were: (1)