NOTES
378
90
il
I
'oo/-
-05
10
,
,
15
20
28,
COPPER
1 25
30
35
K,.
Fig. 1.-X-Ray diffraction patterns of wax ultracentrifuged from crude oil and of commercial, high-melting point wax.
are rather positive proof that the materials centrifuged from crude oils, as described above, are waxes. Their softening points and lack of solubility in solvents such as hydrocarbons and chloroform indicate that they are of relatively high molecular weight. The ease with which these waxes were ultracentrifuged from petroleum indicates that they were present as unstable colloids, probably in a, suspended microcrystalline form. These results indicate that the sediment obtained from ultracentrifugation of petroleum often contains relatively large amounts of wax in addition to the asphaltic materials previously identified.2.3 Such waxes must be taken into account during interpretation of ultracentrifuge data based on sediment obtained. Because the centrifugal forces used axe in the range of supercentrifuges, the centrifugd method may prove commercially applicable for clarification of crude oils or refinery stocks and for the preparation of high-molecularweight waxes.
THE HEATS OF COMBUSTION OF SOME COBALT AMMINE AZIDES B Y TERENCE M.
DONOVAN, c. HOWARD SHOMATE AND TAYLOR B. JOYNER
Chcmislry Divisron, Research Department, U. S., Naval Ordnance Station. Chrna Lake, Cali/ornta. Received October SO, 1960
1881
There has lbeen recent interest in the thermodynamics and kinetics of metallic azides. Previously the heat of formation of thallium azide was determined in this Laboratory.2 During the (1) B. L. Evans. A. D. Yoffe and Peter Gray, Chcm. RwB.. S9, 51.5 (1859).
Vol. 64
course of a study of the thermal decomposition of some cobalt ammine azides it was thought desirable to have values of their heats of formation and the present study resulted. Experimental Materials.-The compounds were prepared and purified by previously described methods.3- X-Ray powder pattrrns were used to identify all compounds except [Co(NH&(N&]. Corroborating evidence of the composition of [Co("&I( N3)3 end .[Co(NH&N3]( N 3 ) 2 was obtained during t.he course of kinet,ic studes of their thermal decomp~sition.~ Explosions prevented similar studies of the remaining compounds. The very explosive [Co(NH3)3(N&] wsw obtained by individual preparations each yielding enough material (a). 400 mg.) for a single combustion. This was carefully washed but, not recrystallized because of the rapid hydrolysis in warm water.' In view of these difficulties, some uncertainty must be attached to the reported AH+ of this compound. Measurements.-The measurements were made with calorimetric equipment described previously.s*9 Bcnzoic acid (N.B.S. sample No. 39g) was used in determining the energy equivalent of the calorimeter which was 2789.36 i 0.43 cal. deg.-' for all determinations. All weighings were reduced to vacuum and all heat values are expressed in defined calories ( I cal. = 4.1&10 abs. joules). X-Ray powder patterns of the solid residues showed the lines of COO and COaOc only, except in the case of [Co(NH3),(N&] where t8he lines of cobalt metal also were evident. Average values of the 0:Co ratios as determined by reducing the residue samples in a stream of HP a t 700" are: [ CO(NHJ)G]( N3)3. 1.1232; [Co[NHs)sNs](N3)2, 1.1577; n's1.1285; tram- [ CO(NH3)4(NB)&s, CO(NH3)4(NI)P]N3, 1.1253; and [Co(NHa)3(Na)s],0.8401. All the energy values were corrected to correspond to cobalt aa the free metal in the final product using 57.1 kcal. mole-' as the heat of formRt,ionof COOand 35.7 kcal. g. atom-' as t.he energy of combination of the excess oxygen.l0 The exhaust gases were tested for oxides of nitrogen and carbon monoxide spectrographically and the bomh washings were tested for soluble cobalt with KOCN. Observat,ion of the bomb wmhings showed no starting material which in all cases except the [Co(NH,)&N3)3] consisted of highly colored water -soluble matenal. A 360-ml. Parr double-valve oxygen bomb with 1 ml. of water waa flushed for 15 minutes m t h oxygen a t slightly greater than atmospheric pressure and then filled to 30 atmospheres for the combust,ions. Corrections were made for the ignition wire and fuse material. The observed values for the heat of the bomb process were corrected to obtain values for the energy of the idealized combustion reaction in which all the reactants and products were in their standard states a t 25" and no external work was performed. The corrections, which included those for the formation of nitric acid, were made as described by Huhbard, Scott and Waddingt0n.l'
Results The determined heats of combustion are: [Co(NHs)~] (Nd3, -645.5 0.3; [Co(",)i"I (N3)z: -562.8 f 0.4; ~ ~ u ~ ~ - [ C O ( N H ~ ) ~ ( N -500.3 ~)Z]~CT~, 0.8; ~ ~ s - [ C O ( N H , ) ~ ( N ~-500.8 ) ~ ] N ~ ,f 0.4,
*
(2) W. S. McEwan and M. M. Williams, J. Am. Chem. Soc., 76, 2182 (1954). (3) M. Linhard and H . Flygare, Z. anorg. allgem. Chem., 262, 328 (1950). (4) M. Linhard and M. Weigel, ibad., 463, 245 (1950). (5) M. Linhard, M . Weigel and H. Flygare, &bid..268, 233 (1950~. (6) T. B. Joyner, D. A. Stewart and L. A. Burkardt. Anal. Chcm., SO, 194 (1958). (7) To he reported by Taylor B . .Ioyner and Frank Verhoek. (8) W. S. McEwan and M . W. Rigg, J. Am. Chem. Soc., 73. 4725 (1951). ( Y ) M. M. Williams, W. S. M c E r a n and R . A Henry, THISJ O U R N A L , 61, 2G1 (1957). ( 1 0 ) B. J. Boyle, F . G. King and K . C. Conway, J. Am. Chem. Sor., 76. 3835 (1954). (11) W. N. Hubbard. D. W. Scott and G . Waddington. THISJonaN L L . 68. 152 (1954).
March, 1960
NOTES TABLEI COMRUSTION DATA Sample wt., g. vacuum
0.9934 1 .OOO6 1.0010 1.0062 0.9889
- AH00
kcnl./mole
AHP. kcal./ inolr
645. G4 644.8G 646.44 644.98 645.76
mean 645.5 f 0 . 3 30.7 [Co(NH3)5N3I( N3)2
1 .oO09 1 .m 0.9998 1.0011 1.0048
562.59 562.73 563.00 5K3.8G 561.70
m c a n 5 6 2 . 8 2 ~0 . 4 5 0 . 4 cis- [Co(NH,),( N2)2 1x3
0.5001 ,5048 ,5109 ,5189 ,4991
500.3G 500.36 500.51 500.42 502.22
mean 500.8 f 0 . 4 9 0 . 9
!rans-[Co(?;H3I4(N.r)21N3 0.4976 ,497: 5118 ,5137 ,5096
502.04 501.70 500.42 499.20 498.03
379
of the rare earth oxides. The method, involving the determination of the heat evolved from the c*oml)ustionof a weighed sample of the metal in a homb calorimeter at a known initial pressure of oxygen, has been d e s c r i b ~ d . ~The same units and conventions are used here. Thulium Metal.-Thiilium metal waa obtained from two sourccs, Ames Laboratory, A.E.C., Ames, Iowa (Ames) and The Michigan Chemical Co., Saint Louis, Michigan (M.C.). The analyses of the samples wcre made a t this Laboratory :ind are summarized in Table I. ANALYSIS O F
TABLE 1 THULIUM hIETAL--yo IMPURITIES
1% 0 N M g Ca Ta Sm 0.009 0 . 0 2 0 0 006 0.04 0.10 .. 1.0 0.075 0 . 0 3 7 0 . 2 3 0 0.009 0.05 0.10 1.05
C
Ames M.C.
0.090
..
No other metallic impurities were detected spectrochemically. The thulium metal from Ames t.hus contained about 1.27% impurities, the M.C. metal, 1.55%. Assuming that the non-metallic impurities were combined with the thulium ;is the carbide, hydride, nitride and oxide, the Ames material was 96.69 mole 7. mctal and the M.C. material, 93.66 mole ‘7..(Atomic weight T m = 168.94.) The X-ray lattice constants for the M.C. material were slightly greater than i.xpected, possibly indicating the presence of rare earths of lower atomic number in solution. Combustion of Thulium.-A 10 mil diameter fuse wire of magnesium was used to ignite the thulium. The thulium WLS burned on sintered discs of thulium oxide in oxygen a t 25 atni. pressure. The metal showed no gain in weight when rlxposed to O2 a t 25 atm. pressure for one hour. Combustion varied from 88.67 to 99.67% of completion. The :hveragc initial temperature was 25.2”. The two series of x1n.s are summarized in Table 11.
mean500.3 i- 0 . 8 90.4
‘co(xH3)3(N8)1j
0.4200 0.4593
TABLE I1
“4.2 402.1
T H E I I E A T OF COMBI:hTION OF ‘ h C L 1 C X
Wt.
mean403 2 f 1 0 95.7
[CoINH3)S(N3)3j, -403.2 f 1.0 kcal. mole-’. The heats of formation of these compounds were calculated using -6E,,316 and -94,050.6 (at. wt. C = 12.011) cal. mole-’ as the heats of formation of water and carbon dioxide, respectively. These values are listed in the last column of Table I. As some difficulty was encountered in obtaining tlomplete combustion preliminary calculations were made of the standard deviation of the mean for each set of determinations and any runs which exceeded the mean value by more than three times the standard deviation were discarded. Because of the difficulties mentioned above in the preparation of‘ [ C ~ ( r \ j H ~ ) ~ ( nand T ~ the j ~ ] fact that {mly two acceptable determinations were made of its heat of’ combustion, the reportrd value should be vonsidered preliminary. THE HEAT OF COMBUSTION OF THULIUM’ BY ELMEX J’. HUBER,JR., EARLL. HEAD.4ND
Mg, nig.
Wt. TninOs.
Joliirs: de.il.
iz.
totdl
70.2
10020.2 10019 3 10017.0 10017.5 10018 2 10014 C i
AT, ’A.
fSnrray from Yirinx, ‘y, j. :., g.
TkV.
from mean
Amrs 2 1404 i 9087 2 3009 I . 7425 2,0488 2 1123
7.00 7.29 5.15 0.94 7 11 bj
13
67.6 5!L0 60.6 33 8 40 8
i.mo 1.1477 1.3117 0.9907 1.1685 > 2060
15.1 10 A
5628.2 5658 1
7.7
5619.2 5625.8 5630 4 5638 9
10.3 15,+
:3.8
AV.
5633.3
Stand. dev.
M.C. 2.2753 1.9130 2.0456 2 . n,?1c, 1 9019 2.2207 2 2905 2 03x5
6.75 7.09 7.31 7.42 A.20
ti 39 A 28
57f;
49.6 46.8 40.1 4~ 3 39 1 39 1 33 1 471;
10014.C, 1.2694 12.5 10013.9 1.0750 1 0 . 5 10013.7 I 1462 11.2 10013.7 1.1353 12 o 10011 9 1.0642 12 5 1onii.g 1.2381 11 7 10010.3 1.2751 :fi 7 10014.1 i.1383 TO5 AV.
Stand. dev.
5508.5 1 7 5530 3 2 0 . 1 5517.3 7 1 5499 4 10.8 5515 1 4 . 9 5505.7 4 ,5 5500 3
9 9
5,5049 519 2
.7 :5
$ 0 3 R5
The two values must be corrected for tlie impwitips present.
This paper is a continuation of the series? reporting measurements of the heats of formation
Correction for Impurities.-The calculated percentage composition of the thulium metal (Ames) by weight is as follows: T m metal, 97.77; TmH2* 0.76; Tm203, 0.16; TmN, 0.08; C, 0.09; Mg, 0.04; Ca, 0.10; Sm, 1.0. The heat) of combustion of this thulium metal correct,ed for impurities is 5,595.4 jouies/g. or 0.67% smaller than t,he un-
This work was done under the auspices of the A.E.C. ( 2 ) See E. .J. Huber. Jr., E. L. Head and C. E. Holley. .Jr., THIS JOCR~AL 61, . 1021 (19.571, for reference to earlier paper8 in the series.
(3) E. J. Huher. Jr., C. 0. Mathews and C. E. Holley, Jr., J . Am. Cham. Soc., 77, 6493 (1955). (4) The specific heat of TrnzOa is estimated as 0.20 i o u l e i d d e g .
CHARLES E. HOLLEY, JR.
L o s Alamos Sctentipc Laboratory of the Universify o f California, Los
Alamos, N e w Mezico Received October $ 1 , 1969
‘1)
