The determination of ammonia and total ionic inorganic nitrogen in sea water

Abstract

(Text-figs. I and 2) 161 Combined inorganic nitrogen occurs in sea water principally as nitrate, nitrite and ammonium ions, the concentrations of which lie in the ranges I-600 mg N03--Njm3, 0'1-5°mg N02--Njm3 and 5-50 mg NH4LNjm3 respectively. Nitrogen occurring in any of these forms is readily assimilable by marine organisms, and its exhaustion in sea water is frequently a growthlimiting factor in the water. This paper describes a method for the determination of the total ionic inorganic nitrogen in sea water, based on preliminary reduction to ammonia followed by separation and estimation of the latter colorimetrically.Riley (1953) has discussed the determination of ammonia in sea water, and has concluded that ammonia is best separated from the water, adjusted to pH 9'2, by distillation under reduced pressure in a current of air as described by Krogh (1934). The distillation process is rather time-consuming and requires a special apparatus. Experiments were therefore carried out to separate the ammonia by diffusion. It was found that the capacity of the concentric microdiffusion cells employed by Conway (1950, p. 8) was too small for the volume of sea water which was necessary if low concentrations of ammonia were to be determined. When diffusion was carried out in the flasks (Fig. I) described by Cavett (1937) for the microdetermination of alcohol in blood, reproducible recoveries of approximately 73 % of added ammonium salt were obtained from 50 ml. of sea water after diffusion at 70°C for 24 h at pH 9'2 (Table I).

Manganese oxide minerals: Crystal structures and economic and environmental significance

“…Ocean Mn nodules typically are brown-black and subsphericalbotroyoidal and consist of concentric layers of primarily Mn and iron oxide minerals. Other minerals commonly found in the nodules include: clay minerals, quartz, apatite, biotite, and feldspars (10). Most Mn nodules have formed around central nuclei that may be carbonate mineral fragments, pumice shards, animal remains, coral fragments, etc.…”

Effects of Salinity on Algal Distribution

“…Ammonia was determined by the diffusion method of Riley and Sinsaheni ( 1957) ; chlorinity by titration of halides with silver nitrate ( American Public Health Association 1955) ; dissolved oxygen by the unmodified Winkler technique (American Public Health Association 1955); hydrogen-ion concentration with a Beckman Model G pH meter ; and phosphate by the colorimetric stannous chloride method (American Public Health Association 1955). Fig.…”

Analytical methods in oceanography I. Inorganic methods

“…Riley (1953) has suggested that distillation under reduced pressure would suppress the breakdown of organics and recommended colorimetric determination by the phenatehypochlorite method to produce indophenol blue. In a later paper Riley and Sinhaseni ( 1957) demonstrated the use of microdfision flasks to separate ammonia from sea water in the presence of a metaborate buf€er at 7OOC. A tedious feature of the above methods is the need to separate the ammonia by distillation.…”