![]() Analytical chemists call this type of titration argentometry. When all the chloride ions are precipitated, the titration ends. The precipitate also contains small amounts of silver bromide and silver iodide. As the silver nitrate is slowly added to salt water, a precipitate of silver chloride (mostly) forms. Before 1980, oceanographers measured salinity using the titration-based method in which silver nitrate was used to determine the concentration of chlorine and bromide ions. Oceanographers usually associate the term “salinity” with a measurement technique used to measure it. Some of these methods are more practical than others and some of them provide more precise results. Salinity can be measured using different methods: utilizing evaporation of seawater, by measuring its conductivity, by measuring water density using a hydrometer, through measuring the refraction of light through seawater using a simple refractometer and by titration of halide ions. The reading is taken when viewing at the glass reticle inside the instrument through the eyepiece. When a drop of seawater is placed between a blue-tinted glass prism and a plastic cover lens, it forms a thin layer that refracts light through an angle that depends on the salinity of the seawater sample. How Salinity Is MeasuredĪ handheld refractometer is a very simple analog device for measuring a liquid’s refractive index. Measuring the water salinity, which is the total concentration of all dissolved salts in water, is a more complicated problem. We all know that temperature can be measured using a thermometer, pressure is measured with a pressure gauge. Salt water density can be determined from known temperature, pressure, and salinity. ![]() Sometimes denser and cooler water can move upward oceanographers call this movement upwelling. It is also possible that a very warm layer with higher salinity will float on a cold layer of lower salinity because the latter is denser. ![]() Less dense water floats on top of more dense layers. This value can change because of the variations in the temperature and salinity in different ocean water layers. The average density of ocean water is 1027 kg/m³. Ocean water is denser than pure water because of various salts dissolved in it. American Bureau of Shipping load line mark showing marks for different water density: TF - tropical fresh water, F - fresh water, T - tropical seawater, S - summer temperature seawater, W - winter temperature seawater
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