which would make an essentially instantaneous and continuous measure- 

 ment of salinity accurate to ±0.01% . Instruments which adequately 

 fulfilled these specifications were produced, but the research was 

 terminated before all of the desired features could be incorporated 

 into a single instrument. Sufficient scientific and engineering data have 

 been obtained from the series of instruments which have been built to 

 permit the design of final or production models." 



E. G. Sandels in 1956 described a radio frequency instrument for the 

 measurement of salinity in estuaries. He stated that he had obtained an 

 accuracy of better than ±0.33%o over a salinity range from 0.2 to 50 % . 



In September 1958 G. L. Huebner reported that Texas A&M was, in 

 fact, using an improved radio frequency salinity measuring instrument. 

 He stated that accuracies to approximately ±0.005%o of salinity and 

 difference determinations between samples of the order of ± 0.001 %o 

 had been attained. 



3. Automatic chlorinity titrator (ACT) 



Another laboratory apparatus, developed at the Scripps Institution 

 of Oceanography, is the automatic chlorinity titrator (ACT). The 

 principle of the ACT lies in electrode reactions and the associated 

 electrode potentials. If a piece of silver wire coated with silver 

 chloride is in contact with a solution in which chloride ions are being 

 precipitated as silver chloride, the potential of the electrode, measured 

 against a suitable reference, will be predictable at all stages of titra- 

 tion and will be related to the volume of silver nitrate added. In the 

 ACT this electrode potential drives a titrating mechanism to the end 

 point, and the volume of added silver nitrate is shown on a counter. 



Although a standard deviation of ± 0.0075 %o of salinity was attributed 

 to this instrument, the ACT has never been generally accepted. Only 

 SIO has successfully built and used it. Around 1954 a model of the 

 ACT was received at the Hydrographic Office but never could be put 

 into successful use without an excessive amount of manpower to operate 

 and maintain it. 



4. Interferometer 



Visitors to the VITYAZ during that ship's visits to San Francisco 

 and Honolulu were shown an interferometer with which the Soviets 

 claim they can determine salinity to ±0.02%o. This technique can be 

 used only in the laboratory. However, its complete independence of 

 electronics makes it especially worthwhile. The principle has been 



IV- 9 



