[ 353 ] 



XII. Thermal Properties of Carbonic Acid at Loiv Temperatures. 



(Second Paper.} 



By C. FKEWEN JENKIN, M.A., M.Inst.C.E., Professor of Engineering Science, Oxford, 

 and D. R PYE, M.A., Fellow of New College, Oxford. 



Communicated lij Sit-- ALFKED EWINC;, K.C.B., F.R.S. 



[PLATE 6.] 

 Keceived March 13, Read May 13, 1915. 



CONTENTS. 



Page 



Introduction 354 



The use of throttling experiments 355 



Description of the experiments 



1. Measurement of the total heat of CO-.; gas 356 



2. Measurement of the total heat of liquid C0> 360 



3. Throttling experiments on superheated gas 362 



Construction of the !</> chart 364 



Appendices 



I. A method of plotting pressure curves in the superheated area of the ti<l> chart 369 



II. A method of plotting I lines in the superheated area of the $</> chart 369 



III. Modifications produced in the #</> chart by a correction in the values accepted for the total 



heat of the liquid CO,. 370 



IV. A method of plotting the results of throttling experiments 371 



V. A method of plotting the gas-limit curve from the results of a line of throttling 



experiments 372 



VI. A method of correcting the results of a throttling experiment for a small departure from 



standard conditions 373 



VII. Allowance for the small drop of pressure in the 1-inch calorimeter when used to measure 



the total heat of the gas 375 



List of papers referred to 375 



Tables 



A. Observations on the total heat of CO- 2 gas 376 



B. Mean specific heats of CO 2 gas at constant pressure for 10 C. intervals 377 



C. Specific heats of CO;, gas at constant pressure 378 



D. Observations on the total heat of liquid C0 2 , 378 



E. Throttling experiments 379 



F. For plotting throttling experiments 381 



VOL. CCXV. A 534. 3 B [Published September 1, 1915. 



