Exposure of parathion to light resulted in the formation of cholin- 
esterase inhibitors chromatographically different from parathion. The 
material resulting from the ultraviolet light treatment was a mixture of 
parathion, paraoxon, S-ethyl parathion, S-phenyl parathion and other oxi- 
dation and degradation products. That the mixture was less subject to 
diazotization and coupling suggested some destruction of the p-nitrophenol 
moiety. Exposure of the three identified products from parathion gave rise 
to many compounds, which did not separate into distinct spots on the chro- 
matogram. Methyl parathion gave rise only to the corresponding paraoxon, 
which in turn gave rise to a less polar compound (302, 482, 626, 814, 815, 
1139, 1267). Exposure of parathion to sunlight gave rise to p-nitrophenol 
(626). Parathion also underwent isomerization at elevated temperatures 
(406). 
Hydrolytic studies indicated there was no catalysis by [H’). For 
parathion: k = 0.047 [OH-] + 4 x 107® min ~! (25°C.) 
and k = 0.14 [OH7] + 1.5 x 107° min7! (35°C.) 
in 0.001N to 0.50N - NaOH 
“50% = 120 days in the absence of alkali (pH <10) (1141). 
Para-nitrophenol, a degradation and hydrolytic product of parathion, 
was degraded by C. simplex. In cultures of pseudomonas with p-nitrophenol, 
hydroquinone and a quinone were reported to be present (575). 
Degradation rates of dusts at various temperatures were fitted to 
Jander's rate equation, when the rate of degradation did not exceed 80% 
(1389). 
kt = [1-(1-a) 2/3}? 
a = reaction rate 
k = degradation rate constant 
t = reaction time 
269 
