168 



Frequently, it is difficult to persuade competent technicians to remain on such 

 routine jobs. Continual education of new men n^ust therefore take place, and a 

 good personnel office and training program are necessary adjuncts to the chem- 

 istry group. 



Attempts have been made to devise methods which eliminate some of the 

 undesirable features of the Knudsen titration. The measurements of the nearly 

 colligative properties of sea water, the application of electrometric methods for 

 the determination of the equivalence point in titrimetric procedures, and niore 

 recently the application of high frequency techniques employing cells with no in- 

 ternal electrodes have been tried. 



The measurement of electrical conductance has considerable appeal be- 

 cause of the relative ease with which an in situ continuous recording instrument 

 can be adapted to the determination. The extensive publications of Jones and 

 his co-workers, Shedlovsky, and Parker and Parker provide adequate guides to 

 the instrumentation of the method. Thomas, Thompson and Utterback (1934) 

 have determined interpolation formulas for specific conductance as a function of 

 chlorinity at five degree intervals in the temperature range 0° to 25°C. Pollak 

 (unpublished results) has found certain minor inconsistencies in the Thomas, 

 Thompson and Utterback formulas which in part may be accounted for by a geo- 

 graphical factor in the conductivity -chlorinity relationship or possibly because 

 some of their samples had been stored in glass containers. Wenner, Smith and 

 Soule (1930) describe a seagoing conductivity instrument which, if judged solely 

 on accuracy and precision, provides data conaparable with that from the Knudsen 

 titration. The instrument was used on the last cruise of the CARNEGIE and on 

 several of the United States Coast Guard ice patrol vessels. Its main disadvan- 

 tage appears to be in the length of time required to attain temperature equilibri- 

 um before the conductivity measurements can be nnade. Samples must remain 

 in the thermostated cells for 15 minutes, and even with the multiple-celled in- 

 struments 30 to 50 measurements per day is the best that can be expected. 



Sea water slowly dissolves glass containers with a resulting increase in 

 total dissolved solids and conductivity but little or no change in halide content. 

 Samples for conductimetric analysis, then, shduld be stored in glass for only 

 relatively short periods. Plastic bottles, available from most chemical sup- 

 ply houses, appear to be well suited for the storage of sea water samples. They 

 not only are unreactive with sea water but are nearly unbreakable, and if not 

 completely filled, will withstand freezing. 



Despite the several shortcomings, the conductance method and particu- 

 larly the Wenner instrument is considered by rany to be superior to other meth- 

 ods for routine chlorinity analyses. 



The salinity-temperature, depth recorder (STD), developed by the Woods 

 Hole Oceanographic Institution and described by Jacobson (1948), provides a 

 continuous trace of those variables on a three channel strip chart recorder. An 

 underwater unit composed of a conductivity cell, a nickel resistance thermome- 

 ter, and a pressure operated depth element is connected by a multiconductor 

 cable to the deckside unit which contains the amplifiers, salinity computing cir- 

 cuit, and the recorder. The recorder provides traces of salinity in two over- 

 lapping ranges, 20 o/OO to 32 o/oo and 28 °/oo to 40 o/oo, temperature in the 

 range 28° to 90°F, and depth in two ranges up to 1200 feet. The lower limit of 

 20 "/oo in the salinity range restricts the usefulness of the instrument in near- 

 shore operations and the design error of 0.3 °/oo in salinity limits its utility in 

 open ocean studies. Nevertheless, it has been used with considerable success 

 in studies in which extreme range and high precision are not needed. The auth- 



