When a bomb of 300 cubic centimeters capacity is filled with oxygen at a pressure of twenty-four atmospheres it will hold about ten grams of the gas, equivalent to a water value of 2.40 grams. Hence the water value of the above system when charged, assuming the bomb to be of the capacity mentioned, is 380.12 grams.
If the cylinder holding the water be made of fiber or other non-conducting substance, its specific heat is best determined by filling it in a known temperature with water at a definite different temperature.
It is advisable to have the water cylinder of such a size as to permit the use of a quantity of water for the total immersion of the bomb which will weigh, with the water value of the apparatus, an even number of grams. In the case above, 2622.28 grams of water placed in the cylinder will make a water value of 3,000 grams, which is one quite convenient for calculation.
565. Computing the Calories of Combustion.—In the preceding paragraph has been given a brief account of the construction of the calorimeter and of the methods of standardizing it and securing the necessary corrections in the data directly obtained in its use. An illustration of the details of computing the calories of combustion taken from the paper of Stohmann, Kleber and Langbein, will be a sufficient guide for the analyst in conducting the combustion and in the use of the data obtained.[582]
Weight of substance burned, 1.07 grams.
Water value of system (water + apparatus), 2,500 grams.
Preliminary thermometric readings, t₁ = 26.8; t₂ = 27.2; t₃ = 27.7; t₄ = 28.1; t₅ = 28.5; tₙ₁ = 28.9.
Thermometric reading after combustion, Θ₁ = 28.9; Θ₂ = 202; Θ₃ = 213; Θ₄ = 214.2; Θₙ = 214.0.
Final thermometric readings, tʹ₁ = 214.0; tʹ₂ = 213.8; tʹ₃ = 213.6; tʹ₄ = 213.5; tʹ₅ = 213.3; tʹ₆ = 213.1; tʹ₇ = 212.9; tʹ₈ = 212.7; tʹ₉ = 212.6; tʹ₁₀ = 212.4; tʹₙ₂ = 212.2.
From the formulas given above the following numerical values are computed: