In striking contrast to the serious debasement of their silver coins, the gold coins of the Romans were maintained at a high standard of fineness throughout imperial times. Fineness is determined by first weighing a coin in air and then weighing it while it is completely submerged in pure water. By subtracting these two weights and dividing the result into the weight of the coin in air, its specific gravity is obtained, this being the ratio of the weight of the coin to the weight of a volume of water equal to the volume of the coin. Pure gold has a specific gravity at room temperature of 19.3, whereas its alloys with silver, copper, or both, have lower specific gravities; the lower the specific gravity the less the proportion of gold in a given alloy.