137 



r- 



The Interdepartmental Board on International Ice Observation 

 and Ice Patrol Derelict Destruction Service, at its meeting in the fall 

 of 1922 requested the Bureau of Standards to receive all apparatus 

 then on hand employed in connection with salinity measurements., 

 and attempt to perfect a mechanical unit which would be a success. 

 Shortly thereafter Mr. E. F. B. Fries, then scientific observer, de- 

 livered the apparatus to Dr. F. Wenner, United States Bureau of 

 Standards, to whom finallj- the design of a successfully operating 

 machine is mainly due. 



At first it was ])reHumed that only minor changes of the a})paratu!? 

 would be required, but a more thorough investigation and study of 

 the problem by tlie bureau made it evident that it would be neces- 

 sary to make an entirely ncAV design, and in the construction use 

 but a few parts of the old apparatus. This accordingly was done; 

 the new instruments contained in a compact two-door wooden cab- 

 inet, 36 inches high. 33 inches across the front, and 13 inches deep, 

 were installed on the cutter Tampa just before she sailed from Bos- 

 ton on ice patrol, March 15, 1923. Because of the shortness of time, 

 hoAvever, between the sailing of the Tampa and the inability ,to pro- 

 cure sea Avater of known salinity in Boston, or vicinity, the 'apparatus 

 could not be thoroughly tested or standardized until after the end 

 of the ice season. 



When the Tampa returned to Boston in July, 1923, the appa- 

 ratus was tested nsing samples of sea water whose salinity had been 

 determined by independent measurements. At that time the appa- 

 ratus was found to be in excellent condition and gave results reliable 

 to as high a degree of precision as is possible by the more tedious 

 titration method. Four sketches, 'a general description, and instruc- 

 tions for use of the apparatus as designed and operated at present 

 follow : 



PURPOSE AND METHOD 



Tlie apparatus is intended to furnisli a quick and reliable means for the 

 determination of the salinity of sea water under conditions existing on ship- 

 board. It was designed and constructed by the Bureau of Standards at the 

 request of Dr. S. W. Stratton, acting as a member of the Interdepartmental 

 Board on International Sei'vice of Ice Observation. Ice Patrol, and Ocean 

 Derelict Destruction. 



It is known that the electrical resistivity of sea water changes as its total 

 salt content is changed either by evaporation or by dilution with rain, snow, 

 or melting ice. Therefore the measurement of the resistivity may be made to 

 serve instead of a titration density measurement, or direct determination 

 of the salt contained : and this is what the apparatus is intended to do. 



The resistivity is measured by a Wheatstone bridge equipment, making use 

 of what is generally called the substitution method. In this method the solu- 

 tions to be measured are placed one after another in the same cell so that the 

 relative conductivities are obtained without a knowledge of the constant of 



