Though a standardised value of 4.1860 J·cal was established in the early 20th century, in the 1920s, it was ultimately realised that the constant is simply the specific heat of water, a quantity that varies with temperature between the values of 4.17 and 4.22 J· g · °C. The change in unit was the result of the demise of the calorie as a unit in physics and chemistry.