THE ELECTRIC SALINITY TESTER 



The ice-patrol bulletins for 1924 and 1925 (Nos. 12 and 13) contain 

 sections ^' ^ devoted to the description and method of operation of 

 the electric apparatus for measuring the conductivity of sea water, 

 providing a ready means of determining the salinity of water samples 

 on shipboard. The United States Bureau of Standards constructed 

 one such apparatus, which was first placed in successful operation 

 the season of 1924, when some 600 odd samples of sea water were 

 tested. Concurrent with the progressive scientific program laid 

 down for the 1926 patrol, which attempts to follow the drift of ice- 

 bergs by keeping an up-to-date current map on board the patrol 

 ship, it became necessary to provide both ships with the apparatus, 

 instead of one as in the past. Salinity determinations during the 

 season of 1926 were thus made immediately after occupying each 

 station and thus we were able to compute the dynamic value, and 

 so to construct a current map on the spot. The new salinity tester 

 was constructed with the cooperation of the Bureau of Standards 

 in time for installation and calibration on board the Tampa before 

 she sailed in March. The old set was placed on board the Modoc, 

 and both machines, it ought to be added, are alike in detail. A total 

 of about 537 salinity determinations were made during the season 

 of 1926, and no difficulties were experienced with the functioning of 

 the apparatus. A conversion table of scale readings to salinities 

 follows, for use in the operation of these or similar sets in the future. 



The scale range of the instrument readings it will be noted extends 

 from to 800. Readings higher than 800 are obtainable by continu- 

 ing the graph of salinities plotted against instrument readings and 

 checked occasionally by an actual test of a sample of known salinity 

 within the discussed range. 



A table of scale readings of the electric salinity tester with the 

 corresponding values of salinity is shown herewith: 



1 U. S. Trea.s. Dept. Bull. No. 12, 1924, pp. 136-147. 

 » U. S. Treas. Dept. BuU. No. 13, 1925 ,pp. 67-69. 



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