Latent heat of fusion of ice . r seven minutes for whichit was usually employed. The measurement of the energy con-sisted of determinations of the current, the potential differencebetween the coil terminals, and the duration. 19 Dickinson and Mueller: New Calorimetric Resistance Thermometers, this Bull.,9, p. 483; 1913. Dickinson, J Latent Heat of Fusion of Ice 243 The method of these measurements has been previously A diagram of the circuits is shown in Figure 5. Thequick break switch (S) served to throw the current into eitherthe heating coil (M) or a rheostat (
Latent heat of fusion of ice . r seven minutes for whichit was usually employed. The measurement of the energy con-sisted of determinations of the current, the potential differencebetween the coil terminals, and the duration. 19 Dickinson and Mueller: New Calorimetric Resistance Thermometers, this Bull.,9, p. 483; 1913. Dickinson, J Latent Heat of Fusion of Ice 243 The method of these measurements has been previously A diagram of the circuits is shown in Figure 5. Thequick break switch (S) served to throw the current into eitherthe heating coil (M) or a rheostat (R) of equal resistance outsidethe calorimeter, and simultaneously to record on the chrono-graph tape the time when the switch was thrown. Measurementsof current and potential difference were taken alternately duringthe period of energy supply, using the switch (K) which connectsthe potentiometer with either the coil or the volt heating coil was of such a resistance (10 ohms) that the TO STORAGE BATTERY(80 VOLTS. TO MASTER CLOCK bwvJ HEATING COILJ06>Ct) SHAPE OF BLADE IN SWITCH SWITH AUTOMATIC CHRONOGRAPH SWITCH. Pig. 5.—Diagram of circuits for electrical method potentiometer settings were very nearly the same for both measure-ments. The mean current, mean potential difference and thetime, the product of which measures the total energy, were eachmeasured to better than 1 part in 20000. In this method the difference in temperature of the calorimeterwater before and after melting the ice was seldom more than o?2 , during the period of melting, on account of the morerapid melting of the ice sample when first introduced, the tempera-ture of the calorimeter fell during the earlier part and rose later.(See Fig. 9.) The shape of the ice sample was chosen with a 17 Dickinson, Mueller, and George: Specific Heat of Calcium Chloride Solutions, this Bull., 6, p. 379;1910. 244 Bulletin of the Bureau of Standards [Vol. 10 view to making the rate of melting as uni
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