METHODS FOR THE DETERMINATION OF DISSOLVED ORGANIC CARBON AND NITROGEN IN SEA WATER

¹ From the Laboratory of Zoöphysiology, Copenhagen University, and the Woods, Hole Oceanographic Institution

A method for the determination of organic nitrogen in solution in sea water is described in detail. The principle of Will-Warrentrap, involving digestion at 500° C. with caustic soda in an atmosphere of hydrogen, is used. The sensitivity of the method is roughly 0.0003 mg. N, giving an accuracy in sea water of about 5 per cent in 5- or 10-ml. samples.

A wet combustion method for the analytical determination of dissolved organic carbon in sea water is presented. Halides are removed with thallous sulphate, the evaporated sea water residue is oxidized by means of ceric-chromic sulphuric acid, and the evolved carbon dioxide eventually determined by acid titration of baryta solution through which the gases have passed. The accuracy approaches 0.1 mg. carbon per liter.

Differentiation between organic matter in colloidal and in true solution is made by analyses before and after ultra-filtration, using "Membranfilter Gesellschaft" collodion filters and a modification of the Thiessen ultrafiltration apparatus.

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