njit-etd1961-002 - New Jersey Institute of Technology

10predicted and given. —over, most of the other methodsare not recommended for values of Zc less than 0.23 orboiling point less than 250 ° K. This method of vaporpressure correlation has ±107 accuracy.In the absence of any experimental data, the heatcapacity data for formaldehyde were calculated byWalker 16 based ou. pectroscopic measurements. Thesedata can be represeroc ,1 by the following equation as afunction of temperature between 0 to 400 ° C.Cp = 9.48 + 0.00914T - 6.4 x 10 -7 T 2The accuracy of the . , boqe equation is not known. However,formaldehyde poss ee no internal rotation and this factmakes the use of the )rincipleD of statistical mechanicspossible for predicting accurate heat capacity andabsolute entropy for the ideal gaseous state fromspectroscopic measurement For this reason, the resultsobtained by using the rIkt.)e heat capacity equation tocalculate the enthalpy ind entropy of the ideal gas arebelieved to have :or y accuracy.The. ,,orrelations of Lydersen, Greenkorn,and Hauge,. wer- n -ied to obtain the values of thespecific volume, ek iJalpy and entropy in both the saturatedand superhcatr, d re. These correlations were basedon the ),,)nding states which pro thatall pure I,I sibility faLf - orsand departui L, ,1 LetHvior of enthalpy andentropy when F14,=,. , , , 0,4,, tomt,-; reclined conditions ofpressure and tic,p ,,n,a and au the value of Zc.The specific volumes of the saturated liquid wereevaluated by the method of Watson 2 .. This method is notsensitive to errors in D c or Zc. The average error inestimating liquid densities by this method is about 1%.