Testing for pH, conductivity and refraction are essential tools. A pH meter is used to measure the acidity or basicity of a liquid, and can be used to measure the pH of water, soil, or other liquids. A conductivity meter is used to measure the ability of a liquid to conduct electricity, usually used to measure the amount of dissolved salts in a liquid which can help determine water quality. A refractometer is used to measure the index of refraction of a liquid, and can be used to determine the concentration of dissolved substances in the liquid.