The avoirdupois pound shall bear to the troy pound the relation of seven thousand to five thousand seven hundred sixty. The hundredweight shall contain one hundred avoirdupois pounds; and the ton, twenty hundredweight. The barrel for liquids shall contain thirty-one and one-half gallons, except the barrel for beer, ale and porter which shall contain thirty-one gallons; and the hogshead, two barrels. The liquid gallon shall contain two hundred thirty-one cubic inches.