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Salinity

Salinity

Salinity is a measurement that has different meanings in different industries. Overall it is a measurement of salts in water. Salts can be measured by electrolytic conductivity (EC), refractometry, titration of chloride, or specifically for sodium chloride using a sodium Ion-Selective Electrode (ISE).

 

Salinity measurements can be broken down into two major forms. Those that are for oceanographic studies for seawater salinity and those for food or brine solutions in which there is a weight/weight or weight/volume relationship.

Titrators

Titrators are available to perform a titration using the silver/sulfide ISE. With this titration the electrode is used as an indicator to follow the progress and detect the endpoint of an argentometric titration of chloride with silver nitrate titrant. During the titration the silver from silver nitrate reacts with the chloride in the sample to form insoluble silver chloride. When chloride is no longer available then silver ions will be in the solution. The ISE follows the increasing silver ion concentration as silver nitrate titrant is added. The stoichiometric end point, a large change in mV occurs. Titration systems are available with one or two analog board inputs and options for one or two dosing pumps.

Benchtop Meters

Benchtop meters include versions that measure salinity by conductivity along with a version that can use an ISE to measure sodium or chloride. A two channel option allows one channel to be used with a pH/ISE probe and the other channel for use with a conductivity sensor to measure salinity. The benchtop meters have the ion charge and formula weight pre-programmed for use with an ISE. The benchtop meters also have incremental methods pre-programmed including the known addition, known subtraction, analyte addition and analyte subtraction methods.

Portable Meters

Portable salinity meters include those that measure salinity by conductivity, ISE, or refractometery. Which scale is available is based on the technology used with conductivity using the seawater scales, ISE then weight/weight or weight/volume, or refractometry that has algorithms for both.

Electrodes & Probes

Salinity probe include the replacement probes for the portable and benchtop meters. These include conductivity sensors, sodium ISE and the silver/sulfide ISE for salt titrations.

Solutions

Solutions for salinity measurement include salinity and sodium chloride standards used for calibration. Also in this category are the maintenance solutions for the ISEs. These solutions include condition, storage, and refill solutions.

Titrants

This category has the titrants and reagents necessary to perform an agentometric salt titration.

Accessories

Accessories include polishing strips for the salinity ISE and magnetic stirrers to ensure adequate mixing when using the ISE.

Chemical Test Kits

A salinity Chemical Test Kit (CTK) is available as a single parameter or with other key parameters for marine studies. The salinity CTK is a simple titration method. For educational use there is the Hanna Backpack Lab for Marine Science and it includes a salinity test kit along with a teacher’s guide that discusses the importance of the parameter.