Buoyancy is reflected by a specific gravity gradient displayed on the stem of the hydrometer. The drop of water is then covered with a translucent cover to help diffuse incident light. The salinometer contains a prism which refracts light into various wavelengths. As salinity of the water changes, the refractive index also changes. This is shown as a line separating a blue and white field of light on a salinity gradient background.
Salinity is determined by observing where the line intersects with the gradient.
The test you will perform is a titration known as the argentometric method. In a neutral or slightly alkaline solution, potassium chromate can indicate the end point of the silver nitrate titration of chloride. Another method we will try is the mercuric thiocyanate method wherein a chloride reacts with mercuric thiocyanate to form mercuric chloride and liberate the thiocyanate ion. Thiocyanate ions react with the ferric ions in a ferric ion solution to form an orange ferric thiocyanate complex. Conductance of a solution is measured between two spatially fixed and chemically inert electrodes.