Noms
Dcc., 1950 teiits which was established within 0.003" by means of a platinum resistance thermometer. The liquid sample within the calorimeter was agitated by a small centrifugal impeller. The energy measurements were made in wattseconds and were converted to mean gram calories by the relation 1 thermochemical calorie = 4.1840 abs. joules The apparatus was calibrated by measurements with water for which accurate thermodynamic data are available. The volume of the gas phase was maintained a t less than 2.5% of the total volume of the calorimeter, and therefore simplifying assumptions in the calculations of the heat capacity from the thermal data are justified a t temperatures below 100°.a The hydrazine-water mixtures were prepared by diluting nearly pure hydrazine with distilled water and by refluxing the mixture a t low pressures to remove dissolved gases. The compositions of the mixtures were determined from the quantity and composition of the hydrazine used and the weight of water added. I t was found as a result of careful chemical analyses that the hydrazine contained less than 0.001 mole fraction of impurities. Analyses of the mixtures were also made and good agreement with the compositions computed from the gravimetric data was realized. Limited decomposition of the mixtures rich in hydrazine was evidenced a t higher temperatures during the heat capacity measurements.
5775
50
i
I
60
70
80
TEMOERATbRE,'C.
Fig. 1.-Isobaric
heat capacity of hydrazine a t bubblepoint pressure.
data for the hydrazine-water system are depicted in Fig. 2. Density measurements were made with
Results Smoothed values of the isobaric heat capacity of the hydrazine-water system a t bubble point are shown in Table I for compositions from 0.5 to 1.0 weight fraction hydrazine in the temperature range from 40 t o 90". The maximum error of the TABLE I SMOOTHED VALUES OF ISOBARIC
HYDRAZINE-WATER SYSTEM Composition wt. fract. ----Isobaric hydrazine 40'
0.50 .60 .70 .80 ,90 1.00 a
HEAT CAPACITIES BUBBLEPOINT
OF
AT
heat capacity, cal./g.,
"e.----
60° 70' 80° 90' 0.8811' 0.860sa 0.8761 0.8943 0 9126 O.930ea ,8546 .8673 .8783 8887a .8351° ,8430' .8152a ,8230" ,8313 ,8404 .8483 .85545 ,7985 ,8057 .8134 .8203 .8258= ,7902 .7796 .7864 .7927 .79875 ,7632 ,7721 .7517 ,7593 ,7665 .7742a ,7368 .7443 50'
.
I 020
,ElSY-
Fig. 2.-Isobaric
These values are extrapolated.
heat capacity data is estimated to be l%,and 75% of the values recorded in Table I probably do not involve uncertainties greater than 0.5%. I n Fig. 1 is presented the heat capacity of pure hydrazine as a function of temperature and, for comparison, data reported in the literature6 for this compound are also included. The smoothed heat capacity L)ENSI.CIES Composition. wt. fract. hydrazine
OF
TABLE I1 HYDRAZINE-WATER MIXTURES Density
7 -
00
50'
.9f)
1.0078 1.0074 1,0063 1,0014
1.0050 1,0046 1.0030 0.9976
0.9925
,9893
1.00
.9816
.9780
0.50 .60 .7u
.80
(6) D. W. Scott, el n l . , ?'HIS J O U K N A L , 71, 22!U (1'910)
0 61
0 7e FRACTI01.
0 83
0 7r
mYDR47INE
heat capacity of the hydrazine-water system.
a pycnometer for a number of mixtures a t compositions between 0.5 and 1.0 weight fraction hydrazine a t temperatures between 0 and 50'. The smoothed data are presented in Table I1 and i t is unlikely that they involve uncertainties larger than
O.ly&
DEPT.OF CHEMICAL ENGINEERING CALIFORNIA INSTITUTEOF TECHNOLOGY PASADENA 4, CALIFORNIA RECEIVED JULY 7, 1'350
Heat Capacities of Several Organic Liquids' BY E. W.
HOUGH,* D.
M. MASONAND B. H. SAGE
The isobaric heat capacities of aniline, ethylenediamine, furfuryl alcohol, isopropylamine, methyl (1) This paper presents the results of one phase of research carried out for the Jet Propulsion Laboratory, California Institute of Technology, under Contract No. W-04-200-ORD-1482sponsored by the U. S. Army Ordnance Department. (2) Stanoliiid Oil and Gas Company, Tulsa, Oklahoma
NOTES
5776
Vol. 72
alcohol and nitromethane were determined in a stainless steel bomb calorimeter at bubble point. The measurements were made a t temperatures from 20 to loo', except for aniline for which the maximum was 180'.
TABLE I REFRACTIVE INDICES OF SAMPLES AT 25' Index of refractiona M easured Literature
Liquid
Aniline 1 5826 1 5863b3c Ethylenediamine 1.4553 1.4552 Experimental Furfuryl alcohol 14831 1 . 4850E The calorimeter used in establishing the heat capacities Isopropylamine 1 3724 1 3720f*d of these liquids and the technique of measurements have Methyl alcohol 1 3270 1.3271' been described in detail elsewhere Essentially, the Methyl alcohol 1 .3267h*f equipment consisted of R vacuum jacket within which a stainless steel bomb-type Calorimeter of approximately 1 Nitromethane 1.3800 1 38Wb liter volume was suspended by small wires. An electrical *Index of refraction relative to the D-lie of sodium. heater was used to raise the temperature of the calorimeter Value a t 20". "International Critical Tables," 7, and contents. The change in temperature was measured 38, McGraw-Hill Book Co., Inc., New York, N. Y., with an uncertainty of 0.003 by means of J platinum re- 1930. J. W. Briihl, 2. pbysik. Chm., 16, 214 (1895). sistance thermometer. The coiltents of the calorimeter e "Handbook of Chemistry and Physics," 31st Ed., were agitated by a s n i d l centrifugal impeller. Integrated Chemical Rubber Publishing Co., Cleveland, Ohio, 1949, values of the energy added to the Calorimeter involved a p. 851. sThese values are extrapolated. 0 J. W. probable error of not more than 0.030/,. The over-all Bruhl and H. Schroder,2. physik. Chem., 50, 10 (1905). accuracy of the apparatus was checked b y measurements J. Timmermans and Mme. Hennaut-Roland, J. chim. with water for which accurate thermodynamic data
