QUANTITATIVE DETERMINATION OF TUNGSTEN AND 

 MOLYBDENUM IN SEA WATER 



By Masayoshi Ishibashi, Tsunebobu Shigematsu 



and Yasuharu Nakagawa 



Kyoto University, Japan 



As an amount of molybdenum in sea water, the values obtained 

 bv Ernst et «/. (1), Bardet et al. (2) and Ishibashi et al. (S) are about 

 0.3, 3 and 10 ^g per kg. of sea water respectively. 



Tungsten has been detected in sea water, but the amount of it is 

 not yet quantified. From the regularities of the amount of elements 

 dissolving in sea water (4), Ishibashi and Shigematsu calculated and pre- 

 sumed the amounts of molybdenum and tungsten dissolved in sea water 

 as about 10 /.tg Mo/1, and 0.4 fig W/1. 



We determined the amounts of molybdenum and tungsten in sea 

 water and found that the amount of molybdenum was almost same as 

 that previously obtained by our thiocyanate method (3), and the amount 

 of tungsten was about 0.1 p.g per 1. of sea water. 



I. COLORIMETRIC DETERMINATION OF TuNGSTEN AND MOLYBDENUISI 



We studied on the colorimetric procedure for trace amounts of 

 tungsten and molybdenum by dithiol (toluene-3,4-dithiol) and estab- 

 lished the conditions necessary and satisfactory to obtain accurate results. 



Reagents: 



Dithiol solution; dissolved 0.2 g. of dithiol in 100 ml. of 7V-NaOH, 

 freshly prepared, or stored under Hg atmosphere. The solution is stable 

 for 2 months under H,. 



Standard tungstate solution; 10 p.g W/ml. and 10.0 /.tg W/ml. 



Standard molybdate solution; 10 /xg Mo/ml. and 10.0 p.g Mo/ml. 



Procedure: 



The solution containing molybdenum and tungsten was diluted to 

 50.0 ml. The 25.0 ml. aliquot of the solution was acidified with 2 ml. 

 cf N-HCl, then 1 ml. of dithiol solution was added to it, and heated 

 •on boiling water for about 10 minutes. After cooling, the resultant 

 dithiol complexes were extracted with 10 ml. of butylacetate. The color 

 intensity of butylacetate solution (Extinction E.,) was measured by using 

 Pulfrich Photometer, the cell length 2 cm., the filter S661. To the 



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