Gallon (Winchester) bushel, originally a cylindrical measure of inches in diameter and 8 inches in depth. That made the dry gallon . The bushel, which like dry quart and pint still sees some use, was later defined to be 2150.42 cubic inches exactly, making its gallon exactly (). In previous centuries, there had been a corn gallon of around 271 to 272 cubic inches. The "wine", "fluid", or "liquid gallon" has been the standard US gallon since the early 19th century. The wine gallon, which some sources relate to the volume occupied by eight medieval merchant pounds of wine, was at
Grains per gallon Grains per gallon The grain per gallon (gpg) is a unit of water hardness defined as 1 grain (64.8 milligrams) of calcium carbonate dissolved in 1 US gallon of water (3.785412 L). It translates into 1 part in about 58,000 parts of water or 17.1 parts per million (ppm). Also called Clark degree (in terms of an imperial gallon). Calcium and magnesium ions present as sulfates, chlorides, carbonates and bicarbonates cause water to be hard. Water chemists measure water impurities in parts per million (ppm). For understandability, hardness ordinarily is expressed in grains of hardness per gallon of water (gpg).