THERMAL PROPERTIES OF CARBONIC ACID AT LOW TEMPERATURES. 363 



Columns 4, 5, 6 and 7 the observed gauge pressures and corresponding absolute 

 pressures. 



Column 8 gives the observed initial temperature. 



Column 9 gives the same temperature + dti (see Appendix VI.). 



Column 10 gives the standard initial temperature. 



Column 11 gives the observed final temperature. 



Column 12 gives the same temperature +dt 2 (Appendix VI.). 



Column 13 gives 2 which is the observed final temperature +dt 2 + dT 2 

 (Appendix VI.). 



The lines of throttle experiments do not all extend over the same range of 

 pressures. 



Lines H, J, K, L, Q and E extend from 600 to 200 Ib. (J misses two lines.) 



M extends from 500-200. 



N 400-200. 



O 300-200. 



M, N and O were limited at their upper ends by the maximum temperature to 

 which the experiments could be carried. Lines S, T, U and V start at 600 but 



Fig. 7. 



observations were only taken on the 200 and 150 curves. They were made to link on 

 the 150 curve, which had been omitted from the earlier experiments. Line P 

 extended from 700 to 600 and 500. This was the only line taken up to 700-lb. 

 pressure. 



These results were plotted on the 6<f> chart in the way explained in Appendix IV. 

 The results for the 700, 600, 500 and 400 pressure curves were found to coincide with 

 the curves already plotted, and the results for the 300, 200 and 150 pressure curves 

 were parallel to the curves already plotted, thus confirming the values of the specific 

 heats used to plot these curves, but indicating that the limit curve required a small 

 shift at pressures below 400 ; the limit curve was accordingly redrawn below the 400 

 curve in the way explained in Appendix V. (see fig. 6), in which the full line represents 



3 c 2 



