The biological importance of the nitrogen cycle in the ocean has long been r&ognized, but studies of the nitrate content of sea water are few owing to the lack of a simple and reliable analytical method. Attempts to develop a satisfactory technique have met with varying degrees of success. E,arly work by HARVEY~ which involvecl the use of reduced strychnine lackecl sufficient convenience and reliability. CHOW AND ROBIN-SON2 developed a polarographic technique which provided sensitivity and precision, but which could not be performed on shipboard so that sea water samples had to be brought to the laboratory for analysis. They also discovered that the polyethylene bottles which were used to preserve frozen sea water samples introduced contaminants which masked the nitrate reduction polarographic wave.
MULLIN AND KILSZY~ developed
the generally adopted technique involving the reduction of nitrate to nitrite with hydrazinc followed by diazotization.
The main disadvantage of this technique lies in the fact that the reduction must be carried out at a constant temperature for at least 8 h and a total reaction time of 2~ h is required for the reduction to reach equilibrium. NELSON,
KURTZ AND IsRAY