1 98 SCIENCE PROGRESS 



of the action of bacteria in altering the composition of the 

 nitrogenous compounds in the sea-water samples. The first 

 exhaustive and reliable determinations of the amount of nitrogen 

 compounds in the sea were made by Natterer : for the Mediter- 

 ranean, the Marmora Sea, and the Red Sea. Natterer's work 

 was very exact. He obtained his water samples from all 

 depths; he made the analyses immediately after collection on 

 board the ship ; and he used the best methods of analysis that 

 had been developed at the time. Generally speaking he found 

 that nitrous and nitric acids were very scarce in sea-water, 

 so scarce that he found it quite impossible to express their 

 abundance quantitatively, and only referred to it as relatively 

 high and so on. But ammonia was more abundant, and by the 

 use of Nessler's reagent Natterer was able to determine the 

 proportion in which this substance occurred in sea-water. It 

 was most abundant in the water from the mud at the sea 

 bottom, and least so at the surface. The average values are : 



In 87 samples there was o'oojy mgr. to o - o6 mgr. per litre of sea-water. 

 » l 9 » » °-o6i „ n o'l „ „ „ 



)) 5 )> )> 0012 ,, ,, o 15 ,, ,, j, 



„ 1 „ „ 032 „ per litre of sea-water. 



Therefore the amount of inorganic nitrogen in the relatively 

 warm water of the Mediterranean seas was very small. 



Not until 1904 were reliable estimations made of the amount 

 of these substances in the colder waters of the northern seas. 

 In that year the German Fishery Investigation steamer Poseidon 

 collected water samples from the North Sea and Baltic during 

 the International Fishery cruises, and these samples were 

 worked out by Raben of Kiel. 2 All precautions which previous 

 experience had shown to be necessary were observed by Raben, 

 and his work appears to be quite unexceptionable. The water 

 was filtered to eliminate planktonic organisms, and was sterilised 

 by the addition of mercuric chloride. A critical examination of 

 the known methods of determination of nitrogen compounds in 

 small quantity was made, and Raben estimated the nitrous and 

 nitric acids and the ammonia separately. The sample was 



1 " Chemische Untersuchungen in ostlichen Mittelmeeres," etc., Ber. d. Comm. 

 Erforsch. d. Ostl. Mittelmeeres, in Denckschr. Akad. IVien, Bd. 56, 60-2, 65, 

 1892-8. 



2 "Quantitative Bestimmung von Stickstoffverbindungen in Meervvassex," Wiss. 

 Meeresimters. Kiel. Komm. Bd. 8, 1905. 



