Calcium chloride. Polarised light micrograph of crystals of calcium chloride (CaCl2) which is used for dust control and as an antifreeze. This chemical occurs naturally as tachyhydrite and also in sea and mineral waters. It is commercially obtained as a by-product of sodium carbonate manufacture. Uses for calcium chloride include dust control, de-icing roads and as an antifreeze both in concrete and in refrigerator plant solutions. Magnification: x25 at 35mm size.