Detection of nucleic acid in the dissolved constituents of sea water has recently been reported by the authors. The dissolved nucleic acids are carried down by in situ precipitated BiSO₄. In the present study for optimisation of recovery of nucleic acid hydrolysate, investigations have been carried out on effects of: quantities of in .si7u precipitated and added

BaSO₄, sodium chloride treatment, temperature and period of hydrolysis and the strength of acid used for hydrolysis. Characteristics of the nucleic acid hydrolysate isolated by adopting the optimum conditions so obtained, are compared with those of standard DNA (calf-thymus). Sea water collected from Bombay Harbour Bay has been found to contain about 20/Mg DNA per litre.