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CHEMICAL MEASUREMENTS* 

 Dayton E. Carritt 



INTRODUCTION 



Chemistry has contributed much to the development of the science of 

 oceanography. Analytical chemistry has contributed the tools and techniques 

 for detecting and measuring the dissolved and suspended constituents in the sea, 

 thereby providing the chemical, physical, biological, and geological branches of 

 the science with a great deal of the raw data that forms the framework of our 

 description of the oceans. The following will be a discussion of the instruments 

 used to carry out the chemical analyses needed in oceanography. Some of the 

 instruments have been designed specifically for oceanographic studies. Others 

 have been developed for use in other fields but appear, at least in principle, to 

 be well suited to oceanographic studies. 



The instrumentation of chemical operations in oceanography presents 

 three problems. The first is concerned with shipboard operation, the second 

 with work ashore, and the third, representing a trend in oceanography that has 

 only recently been developed to any great extent, that of making in situ meas- 

 urements with instruments that are either lowered from a ship or are attached 

 to unattended recording or telemetering devices. 



Since both shipboard and in situ recording or telemetering operations 

 place some serious limitations on chemical procedures and instruments, it may 

 be well to note these limitations here and to refer to them later in evaluating 

 existing and proposed apparatus. Contrasted with a normal shore-based lab- 

 oratory, a seagoing laboratory (recording or telemetering buoys fall into the 

 latter class) has the following distinctive features: 



(a) Non uniform motion along all axes in space with the associated ac- 

 celerations, predominantly those from ship's roll. These vibrations have a 

 spectrum of periods ranging from less than one second to more than fifteen sec- 

 onds, and amplitudes of from fractions of a millimeter to many feet. Instru- 

 ments containing moving parts which respond to these ambient accelerations 

 obviously have limited application. For example, a high sensitivity meter con- 

 taining the usual moving coil galvanometer is generally useless. However, 

 Leeds and Northrup does produce a high sensitivity Marine Galvanometer of this 

 type (L. and N. No. 2255). Ship's motion also limits the number and kind of 

 operations that an analyst can efficiently perform. The simultaneous adjust- 

 ment of two devices is often difficult, whereas, given free hand to serve as an 



* - Contribution No. 10 from the Chesapeake Bay Institute of The Johns 

 Hopkins University. 



