Thermodynamics of Perfect Solutions 307 like mixtures at equal pressures with and without packing. As observed by in their study of the hydrogen-oxygen reaction, packing retards the oxidation at the higher pressures and accelerates it at the lower pressures.
from rains. All handling of apparatus should be done in as cool a place as possible and out of direct sunlight. In direct hot sunlight the end point is vague, and it is difficult and sometimes impossible to obtain reasonable accuracy. Solutions of iodine and starch carried in the field should be protected from light and heat by covering the bottles with thick toweling, which is kept damp with water.
Frequency of DeterminationsAn operator familiar with the manipulation of the apparatus can make one complete determination in about 3 minutes.It is the best practice to make determinations at 4or 5-minute intervals, using the hourly averages for studying the general trend. Such determinations, made at exactly equal
This paper describes the results of measurements of the heat capacity of nickel oxide, NiO, from 68-298.1°K., making use of the calorimeter described in a previous publication.1 From these results the entropy has been evaluated at 298.1°K., and from published heats of formation and heat capacities at higher temperatures the complete thermodynamic properties of the oxide have been derived.Material.-The nickel oxide used was a c. p. Baker analyzed grade containing less than 0.2% of impurities. Microscopic examination (X1000) showed the material to be made up of transparent cubic crystals of uniform size. This is the only form of the pure oxide which has been reported. The powder was dried for several days at 100°, and a sample then showed no ignition loss on heating to bright redness in a platinum crucible. The total charge of nickel oxide used in these measurements was 151.085 g. (in vacuo) or 2.0229 moles. Frequent checks of the calorimeter resistance against the calibrated thermocouple during the heat capacity measurements showed no significant changes in the calibration.
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