BROMINE IN SEA WATER. 81 



DETERMINATION OF BROMINE IN SEA WATER BY 

 FRACTIONAL TITRATION. 



BY F. GUTZKOW. 



Read befon the California Academy of Sciences, February 6tb, 1888. 



This method of quantitative determination of bromine 

 consists of three operations — 



1 — Separation of the bromine as cuprous bromide. 



2 — Conversion of the cuprous bromide into zinc bromide. 



3 — Titration by hypochlorite of sodium. 



1st Operation. — Separation of the hromine as cuprous bro- 

 mide. — I mix 250 c.c. of filtered sea-water from the Pacific 

 Ocean, to which a drop or two of sulphuric acid has been 

 added, with 100 c.c. of a solution containing 25 grm., more 

 or less, of crystallized cupric sulphate. To this clear solu- 

 tion, in which the copper may be assumed to exist as cupric 

 chloride, I add from a graduated glass a solution of ordinary 

 good sodium sulphite, the strength of which I need not 

 know, until the brown flocculent precipitate which each 

 addition produces will dissolve more and more slowly. It 

 is easy to find a point when the brown precipitate has dis- 

 solved by digesting, but the solution remains slightly turbid 

 from shining crystals of cuprous bromide. The separation 

 ot crystals increases rapidly, cuprous chloride being also 

 separated. An excess of sulphite of soda does not matter 

 much. By heating to about 40° C. the green liquid be- 

 comes blue again. Then, after cooling by water, another 

 addition of sodium sulphite is made, say one-third of the 

 volume previously used, again heated until the blue color 

 distinctly reappears (about 70^ C); the flask is once more 

 cooled by water and allowed to settle, after removing any 

 traces of sodium sulphite remaining in the neck by shaking 



•2d Ses., Vol. I. Issued Feb. 28, 1888. 



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