Specific heat of liquid ammonia

III.General description of apparatus and method 399 IV.Theory of methods 401 1. Notation 401 2. Determination of heat added 402 3. Determination of specific heat of saturated liquid 402 4. Determination of specific heat of liquid at constant pressure 403 5. Correlation of the two methods V. Material VI.First method.Measurements under saturation conditions 1 .Experimental details 409 2. Results of measurements 410 VII.Second method.Measurements at constant pressure 1. Experimental details 417 2. Results of measurements 421 VIII.Form of empirical equation for specific heat of the saturated liquid 425 IX. Conclusions X. Summary , 430 Appendix.-Tables of specific heat and heat content 432 vtnDutm]Specific Heat of Liquid Ammonia 399 it can be estimated that the heat capacity between o°and 24 was approximately 15 per cent lower than it would have been under saturation conditions and that between 2 6°a nd 46 °it was about 21 per cent lower.Both the published values and the values recomputed as indicated are shown in Fig. 1 .EHeau and Ennis 3 (1898) also used the method of mixtures between o°and +25 .Nine grams of ammonia in a capsule of 20 cm 3 capacity were used.Dieterici and Drewes 4 (1904) used the Bunsen ice calorimeter.The specimen of ammonia was inclosed in a sealed glass capsule of 1.2 cm 3 capacity.A. J. Wood 5 (191 2) used the method of mixtures with a sample of about 60 g of ammonia.Six experiments were made between 1 6°a nd 20 C. Keyes and Brownlee 6 (191 6) have given an equation based upon unpublished experimental work of Babcock. III. GENERAL DESCRIPTION OF APPARATUS AND METHODIn carrying out the measurements of specific heat of the liquid two independent methods were used.In one method the heat added to a fixed amount confined in the calorimeter and the resulting change in temperature are measured under saturation conditions.By using independent data for the specific volumes of the two phases and for the latent heat of vaporization the corrections for the heat used to change the temperature and amount of vapor present may be determined and the specific heat of the saturated liquid obtained.In the other method the calorimeter is kept full of liquid at a constant pressure above saturation, the heat added to the variable quantity, and the resulting change in temperature measured, due consideration being paid to the amount and temperature of the expelled portion.The result of this method of measurement is to give the specific heat of the liquid at a constant pressure.By using the independent data for the latent heat of pressure variation of the liquid, the specific heat of the saturated liquid may be computed by general thermodynamic formulas, thus giving an independent check on the two methods of measurement.