500
J. R. PARTISGTOS A S D .i. L. WHTSES
research was done under Project SQTXD through the Pnrdue Research Foiindution. REFERESCES CROG,R . d . , AXII HI-ST, H . : J . I'hys. Chelu. 46, 116%( t W ) . MILES.c'. B.. .\si) HI-ST,H . : J . Phys. Clleni. 46, 1346 (1041). ~ X I L L E R . .i.J . . AS])HI-ST,H . : J. P h y s . Chcni. 49, 20 ( 1 9 4 3 , ROSISI, F. D . : J. Wash. .\cad. Sei. 29, 416 (1030). WHITE.W.P.: The J f o d e r n Cnloritt~efci~.Thc Chciuicnl Cntalog C m q x m y , I!it*.,1r.nYork (1928).
THE YBPOR PRESSI-RE OF SITROSTL C H L O R I l ~ E J. R . P l R T I S G T O S
\ X I >-1. L.
WHTSES
Dt-partntent of Cheniistt y, Qiteen .llary College, Uni rc rsi t y of' L o u d o n , London, E . l , England
Rccciced .Ipi 1 1 20, 1948
The vapor pressure of nitrosyl chloriclc at low temperatures has been measured by Briner and Pyllioff (1) and Trautz and Gerwig (41, but their results differ widely over the range -15°C. to -iO"C., the masinium difference being 110 mm. at -45°C. Their results are sho\vn in figure 2 . in which loglop is plotted against (1 T ) X lo4. In view of the discrepancy the determination has been repeat ecl. CxPmIms'r.iL
T o avoid the "tailing" of mercury, Trautz and Gerivig placed 3 thin layer of concentrated sulfuric acid over the mercury in each limb of the U-tube which v a s used as a null instrument. In the apparatus described below (see figure 1 nitrosyl chloride does not come in contart with a mercury siirface, since the pressure is halanced with a glass gauge. AUthoughtaps 6 and i were exposed t o nitrosyl chloride during the measurements, it was found that the vacuum grease used was not attacked for sereral hours. and it was shown that the prec:'cure was not affected hy the gregse by sealing off the tubing on the gauge side of taps 6 and
) 1
-
I .
The pumping system consisted of a mercury vapor pump backed by n Cenco Hyrac pump. Attached t o the former was a qualitative manometer. h liquidair trap prevented any nitrosyl chloride reaching the pumps. .Iny substance condensing could be removed by outlet 14. -Ilarge tap (12) connected the pumps to the main vacuum line. tap 11 \\-as med for nitrosyl chloride fractionation in hulh 13, and the three-way tap 3 for the euacuntion of the spoon gauge: the pressure in the latter was observed by manometer 2 . Pressure in the main h e v-aq measured by manometer 1.
50 1
TAPOR PRESSURE O F NITROSYL CHLORIDE
The nitrosyl chloride hulb 1'7 was connected t o the apparatus by ground joint 20 and held in place hy t\ro small Springs. Rult) I(i. n-hich contained the liquid nitrosyl chloride. wits blown of very thin soda gh-- itlie '*thimble") and placed in n Dewar. The spoon gnugc \vas mntle of ml:i glw- t)ut cnclozetl in :i Pyrex tut)e, joint19 and 20 facilitating eahy rcplacenient in the ca-e of breakage, hut the latter ~ r a sminimized hy including a * 4 i o r t circuit" t a p ti. -in air leak for the gauge' ~ r a smacle by healing on a short length of clrairn-off capillary tubing t o tap .5 The illuminated fine-fiher tip of the spoon gauge \\-as observed t tirough b: microscope fitted with c r o s wires. 'l'hi. microscope vas ndju3ted t o zero before the experiment nnd checked after it* completion. Jfanometers 1 tint1 2 \rere i mm. wide, so that capillizry correction- were unnecess:try. I>ifference* in the columns (h) nere rend to f 0 . 1 nini. on L: I\ ootlen scsle. 9
_-
i -
FIG 1. The vacuum system TEMPERATCRE 1fEASCREJfEST
Two methods of temperature measurement n-ere employed, a toluene thermometer and a chromel-alumel thermocouple, the former having the advantage of responding rapidly t o small changes. The chromel-alumel couple had two junctions, both of which were silver soldered, one at the standard temperature O'C., obtained by melting ice (checked by a standard thermometer for each series of readings). For calibration purposes the following points were used : SI'AXDiRD POIXTS .
~
__
.
E.1I.F .
........
mzs.
(1) Rooiii temperntiire. 1B.O'C.. . . . . . . . . . . . . . . . . . . . . . . . . (2) 3Ielting i c e . . . . . . . . . . . . . . . . . . . . . . . . . . . . . t3j M e l t i n g m e r c u r y . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ( 4 ) Sublimation point of solid carbon diosidc. . . . . . . . . . . . . . .
-0.675 0.0 1.391
2,825
The sublimation point of carbon ciioside n'ns used as described by Scott (3!,
502
J. R. PARTINGTON AXD A . L. IVHI-XES
and corrected for pressure by means of the formula given. The E.M.F.’S were measured by a Tinsley thermoelectric potentiometer and galvanometer. A plot of E.M.F. against temperature gave a rtraight line passing through the origin; these results were checked at intervals but were perfectly reproducible. The lou--temperature junction 11as enclosed in x thin glass sheath, of the same order of thickness as the nitrohyl (ahloride h i l t ) . Ai toluene thermometer was calibrated against the tlierniocouple and a correction curve drawn, which \\-as checked again nitli the foiii standard points. In order t o raise the temperature of the bath, acetone u:i\ hlo~vlyadded while letting air into the gauge by the capillary 21. FRACTIOSATIOS OF THE SITROSTL CHLORIDE
Two samples of nitrosyl chloride were used, one obtained from nitrososulfuric acid and sodium chloride and the other from potassium chloride and nitrogen peroxide. The yapor pressure curves were identical. Trap 1.3 was evacuated by connecting taps 8 and 10 to the main vacuum line and closing tap i . The sample of nitrosyl chloride was distilled into the bulb 17 keeping the latter in liquid air, tap 9 n-as closed, taps 10 and 9 were opened, and nitrosyl chloride was pumped out for 13 min. (still in liquid air). After closing tap 11 and opening 8 the Devar was removed from hulb 1’7 and placed around trap 13 so that a quantity of nitrosyl chloride sublimed over; this was again pumped out and about half was distilled back into bulb l i . Taps 9 and 10 were closed and the bulb disconnected. In this way a sample of nitrosyl chloride free from dissolved nitric o d e \\-as introduced into trap 15. PROCKD17€W
Closing taps i and 8 but n i t h taps 3 , 4,3, A, and 11 connected to the main line, the system \\-as pumped out for 15 min. Taps 5 and 6 \\-ere then closed. Manometers 1 and 2 then stood at the same height and the spoon gauge was adjusted to zero. **Thimble" 16 \\-as cooled in liquid air and half of the nitrosyl chloride from trap 15 \\-as distilled over. T a p i was then closed and the gauge brought to zero by admitting air through the capillary 21 and the three-way tap 5 . The small difference in columns 1 and 2 thus corresponds to the vapor pressure of nitrosyl chloride in liquid air. The Dewar from bulb 16 was replaced by an acetone-carbon dioxide bath at -75°C. and more air admitted through the leak. -icetone was then added to the bath until the temperature was -70°C. and measurements were hegun after 5 min. The fiber of the spoon gauge n-as then adjusted to zero, the E.M.F. of the thermocouple was measured, the temperature given by the toluene thermometer was noted, and the difference in the mercury columns (h) was read off. I n this way about 40 thermometer and 20 thermocouple readings were taken over the range -70°C. to -15°C. ‘rap 3 was then closed, tap 6 was opened, and bulb 16 was again cooled in liquid air. After opening tap 3 and pumping out, a further quantity of nitrosyl chloride was distilled from trap 15 into bulb 16. In this way the vapor pressure of a different fraction was obtained and found to be identical with that of the previous one.
503
VhPOR PRESSURE O F KITROSYL CHLORIDE ACCURACY AXD SENSITIVITY
The thermometer and thermocouple are regarded as accurate t o 0.1"C. and the manometer readings to 0.1 mm.; however, the spoon gauge was only sensitivc to 0.3 nini. of mercury. CORRECTIOSS
The manometer readings have been corrected t o O T . and latitude 45- (no correction was necessary for sea level) by formulae given ljy Reilly and Rae (2). DIbCYSbIOS
The results are shon-n in tahle 1 and are plotted in hgure 2 for comparison TI ith those of Trautz and Gern-ig. and of Briner and Pylkoff. Small differences hetween the results of Trautz and Gernig ant1 those of the present work may be
- TO -65.8 -59.6 -56.2 -52.5 -49.2 -47.5 -45.4 -42.8 -40.1 -36.1
20.6 27.5 41.2 51 3 64.5 S0.6 85.4 99.2 117.6 136.4 1TO. 1
0.7 0 5 -0.3 -0 3 -0.5 0.6 -0.5 -0.5 0.6 0.2 -0.2
I
-31.5 -29.7 -27.1 -24.2 -21.3 -20.0 -1s 5
160.0 215.9 237.5 272.7 314 8 360.1 3s3.3 412.1 434.7 462.7 490.1
' 1
1
i1
-0.3 -0.8 -0.2 0.4 0.i -0.5 -0.4 0 0.2 0.3 -0.8
due to dissolved nitric oxide or chlorine, since the former experimenters prepared nitrosyl chloride by passing nitric oxide through liquid chlorine. -1ssurning the vapor t o obey the gas laws and neglecting the volume of the liquid in comparison with the \*olume of the vapor. the Clausius-Clapeyron equation gives :
Le = latent heat of vaporization per gram-molecule L, = - (slope X 2.303 X 1.986) From equation 1, by plotting log p against (l/T) X lo4 a straight line is obtained (figure 2). The x-apor pressure curve of Trautz and Gerir-ig was represented by
+ 7.867
log p (m.Hg) = -1332
T
504
J. R. PARTINGTOS AND A. L . WHYXEB
and the molar heat of vaporization for this temperature range is
L e = GO91 g.-cal. (Briner and Pylkoff gave Le = 3.36 kg.-csl.)
2.8 2.7
2.5
-
2.6
-
2.6
2.3 2.2 2.1 2.0
-
1.9 1.8
1.7 1.6
-!-
a
-
PRESENTWORK TRAVTZ +GERW~G
A 6 R / N f R fPYLKOFF
1.5
I. 2
38
39
40
41
62
63
44
FIG.2 . Plrit of log p
45
4 & 47
48
G?
50
L AxfC'
7-
(iiim.j against (1/T) X 10'
From the rapor pressure measurements described above it is seen that the equation - 1320 T.802 from T 203" to 2.38" loglo p (mm.Hg) = T fits the experimental points (difference.; arc given in tnhle 1) and leads t o an xver~
+-
ELECTROLYTES .\SD ELECTRO('HEMIC.\L
('OUPLES
505
age latent heat of evaporation over this temperature range of 6OG8 g.-cal., 'mole. This is in good agreement with equation 2 of Trautz and Gern-ig.
We wish t o thank Dr. R . F. Hudson for help with the apparatus employed in rhis study-. XEFERESCES : 1 I B R I S E R lf, , E . , ASD P Y L K O F FZ,. : J:chim.
phys. 10, 610 (1912). ('7; R E I L L YR., , ASD R A E ,W.S.: Physicochemical X e t h o d s , T-01. 1, p. 564. l I e t h u e n a n d Company, L t d . , London (1943). , 3 i SCOTT,R . B.: J. Research S a t l . Bur. Standards 25,459 (1940). (4) TRAL-TZ. AI,, . ~ S D GERWIG,IT.: Z . anorg. Chcm. 134,409 (1924).
SOME FUXDA;\IESTAL STUDIES OF ELECTROLYTES ;1SD ELECTROCHEhlIC,IL COUPLES OYER THE TEXIPERATVRE R A S G E 25°C. TO -75°C. -1.B. G - I R R E T T , JhT WELSH, SAMUEL WOODRITFF, ROBERT COOPER, ASD
J O H S HEIICS
Department of Chemisiry, The Ohio S t a t e L-niueisity, Columbus 10, Ohio R e w i r e d July l Y , 1948
The purpose of this paper is to give a preview of the results 1.i-hichhave been obtained to date in our invest'igations of the characterist'ics of electrolytes and These electrochemical couples over the temperature range of 25°C. to -75°C. investigations include: ( 1 ) a study of the physical properties of solvent-electroIyte systems that' remain liquid over this temperature range; (2) the measurement' of voltage and flash current, of several hundred electrochemical couples; (31 the measurement of the polarization of numerous metals and oxidizing agents; and (4)the measurement of the rate of solution of zinc, cadmium, and magnesium in acid solutions. One of t,he main objectives of this ~ v o r k is l to describe the parameters involved ;n developing a primary battery that, i d 1 operate at -T3"C. SOLTEST-ELECTROLYTE SYSTEMS
The systems chosen for study here vere those which would have ( 1 ) a lo~v freezing point, (2) a reasonably high clielect'ric constant, and electrical conducI ii-ky, ( 3 ) lon- volatility at ordinary temperature, and ( 4 ) good solvent characieristics. These qualifications practically restrict the choice of the solvent to :t -rater system. The systems given in tahle 1 are found to offer good possibilities. This ~ o r was k initiated and is supported by t h e Battery Branch of t h e Squier Laboriiof t h e Signal Corps of the P n i t e t l States Army :it Fort lIonniout11, SCVI. Jersey. The r r s u l t s will be published in niow detail later. This pnper w~ispresented a t t h e Sy-niposium o n Gnlvanic Cells a i d Batteries which W:LS Lcld under t h e auspices of t h e Division of Physic:il and Inorganic Chemistry a t the 113th J l r e t i n g of the .iniericon Chemical Society, C'hicago, Illinois, d p r i l , 194'3. tiirg
