(6j Matheson, L. A., and Goggin; W.’C., IND.ENG.CHEM.,31, 334
ACKNOWLEDGMENT
IlO3O). \ - - - - ,
Grateful acknowledgment is made to A. V. Tobolsky and N. Vasileff for encouragement and assistance. The authors also %?ishto thank the members of the of the plastics Laboratory for helpful advice and H. R. Robinson for aSSiSt,ancein Preparing the graphs.
(7) Tobolsky, A. V., Prettyman, I. B., and Dillon, J. H., J. Applied Phys., 15, 380 (1944). RECEIVED August 3. 1948. T h e work described here was sponsored b y the U. S. Army Signal Corps, Bureau of Ships, Bureau of Aeronautics, Bureau of Ordnance, and Office of Naval Research, under Contract W-36-039-SC-
32011.
Properties of Technically Important Hexavalent Chromium Compounds WINSLOW H. HARTFORD Mutual Chemical Company of iimerica, Baltimore, M d . Data are lacking on many physical properties of th,e principal industrial chromium compounds and their aqueous solutions, and are based on impure material or obsolete technique in other cases. Questionable published values have been checked, and many new data are presented in this paper to give reliable information on the following properties of sodium, potassium, and ammonium dichromates, sodium and potassium chromates, and chromium trioxide (chromic acid): physical appearance and crystal structure, density of the solid, melting point of the solid, transition points between hydrates, eutectic with water, solubility in water, freezing point of aqueous solutions, density of aqueous solutions and its variation with temperature, pH of solutions, heat capacity of solutions, and viscosity of solutions. A comprehensive bibliography is included.
T
HE following chromium compounds are produced in quantity and their properties are considered in this paper. Sodium dichromate, Nadh07.2HzO Potassium dichromate, K2Cr~07 Ammonium dichromate, (NH4)&rzO1 Sodium chromate, Na2Ci-04 Potassium chromate, KzCrOa Chromium trioxide (chromic acid), ‘ 2 1 . 0 3
.
pounds are now produced in grades of comparable purity, so that the availability of pure material is no longer a problem. Investigation of the literature indicates t h a t much of it is old and t h a t some earlier workers employed techniques which are now obsolete. The more reliable of these data, after checking, were combined with unpublished measurements in 1941 to give a fairly complete privately printed source of information ( 4 8 ) on solubility, density, pH, freezing and boiling points of solutions, and various properties of the solids. A similar publication appeared in 1933 (68)but was much less comprehensive. With the availability of pure materials and improved techniques, i t appeared advisable to check the evisting data and t o supplement them with additional measurements. The following properties have been critically examined and new data obtained wherever it appeared necessary: Physical a pearance and crystal structure Density o&he solid Melting point of the solid Transition points between hydrates Eutectic with water D a t a for the system salt-water (solubility, freezing point) Density of solutions, and its variation with temperature p H of solutions Heat capacity of solutions 10. Viscosity of solutions 1. 2. 3. 4. 5. 6. 7. 8. 9.
METHODS EMPLOYED
The most important of the six compounds listed is sodium dichromate, b u t the usual reference works (26, 35, 38, 62, 7 2 ) contain sketchy and inaccurate notes on many of its properties because a t the time much of the classical work was being done, sodium dichromate was not available in a state sufficiently pure for investigation. The present technical grade may have the following analysis: Total Cr as NazCr20,.2H20 c1
so4
% of Cr present as -\u’a#2rOa
99.8% 0 06% 0.20% 0.20%
and a C.P. grade is regularly produced, in which impurities are reduced to the amount required by AMERICAN CHEMICAL SOCIETY specifications for potassium dichromate ( 4 ) . The other com-
APPEARANCE AND CRYSTAL STRUCTURE.Little experimental work was required here. Descriptions of the various materials have been revised t o conform t o present production standards and t o eliminate statements obviously based on examination of impure materials. Some crystal constants have been recalculated t o conform t o a uniform convention. DENSITY OF THE SOLID.This constant was determined by pycnometer measurements a t laboratory temperature, using as the immersion liquid, toluene or refined kerosene, both of which are inert toward most hexavalent chromium compounds a t ordinary temperatures. MELTING POINT OF THE SOLID. These data were determined by observing thermal breaks as the material cooled and heated through the melting point, using a calibrated thermocouple and recording potentiometer. I n the case of chromic acid, supplemental data were obtained from manufacturing experience. TRANSITION POINTS. Transition points between hydrates in aqueous solution were determined by measuring the thermal
INDUSTRIAL AND ENGINEERING CHEMISTRY
1994
TABLEI. TYPICAL ANALYSES OF SaLCrzOr
Compound Assay, 70, min. SOa, yo,max. C1, %, niax. Fe, A l , %, max. Ca, %, max. Insol., %, max. Other imourities, %, max.
2H20
-
99.90 0.007
o.ooj
n:ooS 0.001 , ,
.
C.P.
K?Crz07 (NHa)zCrzOi NazCrO4 99.90 99.83 99.90 0.01 0.005 0.01 o.noj 0.005 0 . 005 0.002 0 . no2 ... 0.005 0,005 0.005 0:002 0.01 0.01 S a 0,15 alk. 0.10 saltsa alkali h
K2CrOa 99.90 0.05 n ,005 0 002 0 , no5 0.005 0 . 0 1 iYa 0.08 alkalib
break when 2 to 3 kg of the material werc heated or cooled slowly through the transition range in equilibrium with the saturated solution, using a thermometer accurate t o 0.1O C. Transitions of the anhydrous solids are not a t present of industrial importance and were not checked. EUTECTIC WITH WATER. These data have been obtained in the same way as the transition points, using differential thermometers where feasible; the liquid phase was then analyzed when equilibrium was reached as described below. SYSTEMS WITH WATER(Solubility D a t a ) . Data where the salt is the solid phase have been determined by agitating about 8 liters of saturated solution with excess salt a t constant temperature in a container protected from evaporation After equilibrium is reached, duplicate samples are withdrawn by means of a sinteredglass funnel of appropriate porositv and ti ansferred to weighing bottles for analysis Where the solid phase is ice, the ice point has been determined by studv of the cooling curve of a solution of known analysis. DENSITYOF SOLUTIONS.These were usually obtained by weighing analyzcd solut,ions in a pycnometer a t a determined temperature, Because of the importance of the Baume scale in industrial work, density has bcen calculatcd as dig:", corresponding t o the Baumk reference t,emperature of 60' F. VARIATION O F DENSITYWITH TEJIPERATURE. Determinations were made by use of the pycnometer a t various temperatures and also by the use of Babcock bottles havinq a graduated neck. These graduations were calibrated with water, then weighed samples of solution were placed in the bottles in a wat,er bat,h which was slowly heated. The top of the bottle was covered with a Bunsen valve to prevent evapornt,ion. The height of solution in the graduated neck was observed as the temperature changed. By this means, i t was possible to obtain a series of reading. for a single solution without reweighing. Densities obtained by this method c,hecked within about 0.0002 in multiple runs on t,he same solution. pH OF SOLUTIONS.p H of solutions were obtained with a Beckinan Model G meter, a t 25" C. Readings checked within 0.02 pH in all cases. Care was taken in the case of the bichromat,es to use materials containing no free CrOa or chromate, a i shown by establishment of the pH-titrat'ion curve for each salt. For the chromates, considerably more difficulty was noted because of the sensitivity of these solutions to atmospheric carbon dioxide. The values given are for freshly recrystallized samples in freshly distilled water. HEATCAPACITY OF SOLUTIONS.A modification of the method of TSTilliams ( 8 6 ) n'as emdoyed, using a differential thermometer, calibrated precision ammeter, and potentiometer as instruments. Runs were made in triplicate, and results were duplicable to within an average of +0.002 cal. per gram per ' C. VISCOSITYOF SOLUTIONS.The Ostwald type of viscometer and a constant temperature bath were employed. Results were reproducible to +0.02 centipoise.
Compound Formula Color Crystal habit Cr stal system u class Axial ratio (a:b:c)
s %
PHYsICaL
~\IATERIALS EMPLOYED.The materials used were C.P. materials of the formulas indicated, except where otherwise noted. Analyses of typical CrOs materials are given in Table I. 9Y . 9 0 0,001 METHODSOF AXALYSIS. Solutions employed 0,008 or obtained in the various determinations were 0.02 analyzed by determining the hexavalent chromium 0 , 065 0 . 1 0 a1,k. content by potentiometric titration, using a Kelley salts titration apparatus, and ferrous sulfate solution standardized against twice recrystallized and carefullv dried C.P. potassium dichromate. PRE~ENTATIOT OF DATA. I n properties 1 through 5 above, the values obtained are singlevalued properties. The author has endeavored to give the best possible value for each constant in the light of his own results and those of others, a t the same time giving all values obtained in the present work. The special importance of propertv 6, the system salt-water, has made it desirable to include smoothed data for the systems as well as new data obtained in connection with this paper. In properties 7 through 10, only new information obtained in the present work is presented, with comments on correlation with the literature. Previous work of this laboratory on the pI1 of solutions of sodium dichromate ( 3 0 ) and chromic acid (26) and the density of sodium dichromate solutions (6) is not reprinted.
MATERIALSEMPLOYED
a Determined as sulfates. b As NaO1-I; based on phenolphthalein titration.
TABLE 11.
EXPERIMENTAL RESULTS
. P H Y S I C A L APPESRANCE AND CRYSTAL STRUCTURE. Data On these properties are given in Table IT. The colors given are representative of the pure commercial products; brownish shades reported in the early literature are due to t,he presence of impurities, largely trivalent chromium. The compounds are usually available as granular crystals, with the exception of sodium chromate, which is a fine crystalline powder, and chromium trioxide (chromic acid), which is marketed as flakes prepared from the molten material. Agreement on crystal syst,em and constants is good. The data have been recalculated to follow the conventions of Donnag (IO)regarding asial const,ant,sand angles. The data of Rliinzing ( 4 7 ) for sodium dichromate were obtained on atypical c~ystals and should be rephced by the ~-alue;lgiven, ivhich show better values for t,he face indexes. DENSITYor THE SOLID. The most probable v;ilues for the densities of the solids are given in Table 111. The author has been unsble t o check the value of 2.5246 at, 13" C. given by Stanley ( 7 5 ) for the density of sodium dichromate dihydrate. In view of the impure material availahle zit that time, it is his belief that this value should be reject)ed. Tho present value is the average of three check determinations agreeing within *0.005. Numerous values are available for potassium dichromate. The x-ray data (18) have also been utilized to give a calculated density of 2.678, while the International Critical Tables ( 6 2 ) give 2.69. A value of 2.673 has been obtained in this laboratory.
APPEARANCE B N D CRYSTAL STRUCTURE
Sodium Dichromate NazCr107.2HzO Bright orange Elongated prismatic Monoclinic Sphenoidal 0 5 9 1 2 : l : O 5698
Vol. 41, No. 9
Potassium Dichromate
= 9800' = 90'51' y = 96'13'
O F HEX.4VALENT CHROMIGX C O M P O C S D S
Ammonium Dichromate (N,Ha)zCrzO? Bright red-orange Prismatic Monoclinic Prismatic 1.7665:1:1.0271
Sodium
Potassium Chromate
C hromate NazCrOa Yellow Prismat,ic Orthorhombic Bip yrainidal 0.799i:i:0.4643
KzCrOa
Yellow Prismatic Orthorhombic Bipyramidal 0.7~18:1:0.6694
Ly
Axial inclination Stability in air
94'55' Deliquescent
References
( 2 1 , 84)
@ =
6
Stable
p = 93042' Stable
(18, 68)
(18, 60,6 8 , 81, 8 5 )
Delicluescent moist air ('77)
in
Stable (6,42)
Chromium Trioxide CrOa Dark red Prismatic Orthorhombic Bip yramidal 0.692:1:0.628
INDUSTRIAL AND ENGINEERING CHEMISTRY
September 1949
1995
transition of sodium chromate tatrahydrate to the anhydrous salt;
TABLE 111. DENSITIES OF HEXAVALENT CHROMIUM COMPOUNDS, checking of the point in this laboratory gives the value 63.0 '. REFERRED TO WATERAT 4" C. Potassium chromate tetrahydrate has been reported (6W),a s Formula of Density Temperature, has CrOa.I.120 (H2Cr04) (43). It is very doubtful whether Compound of Solid c. References NanCrz07.2HzO KzCrzOi (NHdzCr207 NazCrOa KzCr04 CrOs
2.348 2.670 2.155 2.723 2.732 2.7
25 25 25 25 18
..
(18, 29, 6?,'68, 68, 7 18, 34, 88)
b\
,Yf)
either compound exists. EUTECTIC WITH WATER. Values for the eutectic composition and temperature with water are given in Table VI.
(62) (62)
TABLE VI. EUTECTIC TEMPERATURES A N D COMPOSITIONS
*
In the case of ammonium dichromate, x-ray data and the two published values are all in good agreement. X-ray data on sodium chromate ( 4 1 ) support the cited figures within 0.007. Of the numerous values for potassium chromate, that given by the International Critical Tables seems to be acceptable. Determination of the density of chromium trioxide presents a considerable problem because of the deliquescence and chemical reactivity of this material. For this reason, the value accurate to 0.1 as reported by the International Critical Tables is probably as satisfactory as can be obtained without recourse to special equipment and immersion liquids. MELTINGPOINT OF THE SOLID. Melting points of the compounds are given in Table IV.
Eutectic Temperature,
Formula of Compound NazCra07.2Hz0 KzCraOr (NH4)zCrzOi NazCrOa KzCrOa CrOa
0
c.
-48.2 -0.63 -2.51 -4.9 -11.3
...
Eutectic Composition, Yo by Weight 69.0 4.3 13.63 20.0 36.1
...
References (28) (52) 86) (8, k0, 32) (6, $2,34)
(5 .;!
These data appear consistent with the solubility and freezing point curves. Information on ammonium dichromate is being presented for the first time. The freezing point curve for chromium trioxide has been investigated, but the only eutectic temperatures reported are the result of extrapolation. Temperatures of - 109" and - 155" C. have been reported. The authors' examination of the data leads to the conclusion that the eutectic TABLEIv. MELTING P O I N T S OF ANHYDROUS HEXAVALENT temperature is about -113" C. and the eutectic composition near 57.7y0 chromium trioxide. CHROMIUX COMPOUNDS PHASERELATIONSHIPS WITH WATER. These relationships Formula of Melting Point, c. References Compound have been well established for the most part. The literature has NazCrtOi 356.7 (56) been examined and the more reliable data indicated by the followXeCrzOi 398 (19, 66,63, 66) ing references: (NH4)zCrzOr Decomposes ... NazCrOa KzCrO4 CrOs
792
971 197
'iQ'68 79) {IO: B6j
Compound
References
NazCrzOi.2HzO
KzCrzO7
*
I
The value for sodium dichromate has been confirmed; the earlier value of 320 C. ( 7 6 )should be discarded. For potassium dichromate, the value given by the International Critical Tables, from the cited data, is satisfactory. There is a transition to the monoclinic form at 241.6' C. (36). Because ammonium dichromate starts to decompose without melting at 180' C., and the reaction, giving principally nitrogen, water vapor, and chromic oxide, becomes self-sustaining a t 225 O C., no figure can be established for its melting point. Sodium chromate undergoes a transition a t 413" C. (1.4) to a hexagonal form, which melts a t the figure given in Table IV. This value has been confirmed in this laboratory. The value for potassium chromate is probably accurate only to *2", being the average of the three sources cited, t w o of which are likewise composite results. The melting point of chromium trioxide is supported by measurements made during the fusion process and by the fairly close agreement of the references. The figure cannot be obtained with the highest accuracy because of the appreciable decomposition of this compound at its melting point. TRANSITION TEMPERATURES OF HYDRATES. D a t a on transition temperatures are shown in Table V. The temperature given for the transition of sodium dichromate dihydrate to the anhydrous salt has been further verified in this laboratory. Values as high as 68" have been reported for the
TABLE V. TRANSITION POINTS OF HYDRATES Transition From NaKhOi.2HzO NazCr04.10HzO NazCrOa.6HnO NazCrOa.4HzO NazCrOa.lOHz0
To Na~CrzOi NazCrOa.6HxO Na2Cr04.4HzO NazCrOa NaxCrOc4HzO(metastable)
Temp.,
' C.
84.6
References (28)
63.0 19,987
(49, 60, 61, 61) (49, 60, 61)
g;j
(NHa)rCreOr NanCrOa CrOs
All these data are in reasonable agreement. For potassium chromate, however, there are rather wide variations between the numerous solubility determinations ( 1 , 3, 8, 9, 12, 15, 21, 24, 31-33, 40, 46,55, 66,69, 70, 73, 7 6 ) . The standard reference works (38, 59, 7 3 ) have reported averaged curves. New points were therefore determined over the usual temperature range, with the following results: Temperature, 1.0 24.0 50.0 80.0
C
% KnCrOa by Weight 37.22 39.39 41.30 43.60
These data agree fairly closely with the curve selected by a trade publication ( 4 8 ) and one of the earlier solubility determinations (55), and align with the eutectic point (see above). The results obtained checked with a maximum deviation of 0.05%; in two cases exact checks were obtained on duplicate samples. On the basis of a careful examination of the above data, the authors believe that the smoothed data given in Tables VI1 and VI11 are most acceptable for the phase relationships of these compounds with water. Transition points and eutectic temperatures are given above. For convenience, freezing point is given as a function of composition in Table VII, solubility as a function of temperature in Table VIII. The solubility of potassium dichromate and ammonium dichromate is slight a t low temperatures, and the maximum freezing point lowering therefore small. DENSITYOF AQUEOUSSOLUTIONS.New data presented in Table I X confirm and extend the previously published data,
1996
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 41, No. 9
indicated by reference numbers in the table. For sodium dichromate, recent data from this laboratory ( 2 ) confirm privately printed data ( @ , 5 8 ) and should supersede the older data of % by CrOi SazC1307 2Hz0 K;CrOa SaiCIOa Stanley ( 7 6 ) on which the present published compilations (2.7, Weight Frwxlng polnt, C. 35, 6 2 ) are based. 10 -3 0 -1.i -1.8 -2 . 1 20 -7.9 -3.6 -4 4 VARIATION OF DENSITY WITH TLVPERATURE. Table X gives 30 -15 4 -6.0 -9 o data obtained in this laboratory for the average variation of 40 -26.8 -9.6 . . 50 -45.3 -15.1 ... density a i t h temperature over the range 15.6" to 50" C. [the 60 ... -26.6 densities selected correspond to even values of Baumi: a t 15.6"C. (60" F.)]. The values given extrapolate to an average value of 30 X for water in this range, which checks the accepted figure closely. The values given are probably accurate to * 2 x 10-6. pH OB?SOLUTIOKS.New data for the pH of solutions are given 0 p 60 4.3 15.16 24 2 1 0 37 14 61.70 in Table XI. 10 (1.67 62 08 7.8 21.06 32.110 38 05 Additional data for sodium dichromate a t higher concentra20 11 . 7 73.18 44.36 62.49 26.67 38.96 30 75,00 16.1 31.98 62.91 46.8' 39.80 tions (SO) and for chromium trioxide ( 2 2 ) ha\Te been published. 40 77.09 36.99 20.9 63,39 48.81 40.61 50 79.46 41.72 26.0 5l.OP 63.90 41.40 Potentiometric titration of a sodium chromate solution in this 60 46.14 31.3 53.54 82.04 64.46 42.15 laboratory gives a value of 9.53 for the true equivalence point io 84.98 50.27 55.2 42.88 36.6 65.08 80 88.39 42.0 65.79 54.10 55.5 43. 60 a t 200 grams of sodium chromate per liter a t 25" C. The values 90 90 60° 66.59 55.8 44.31 9 . 5 57.65 100 91.433 J0 2 56.1 45,00 60.89 67.46 given above are for fresh solutions of recrystallized tetrahydrate in distilled water. a Kumber of moiecules of a a t e r of crystallization in stable phase is indioated by superscript when it differs from formula given. HEAT CAPACITYOF SOLUTIONS. Data on the heat capacity of solutions of sodium chromate (J?'), potassium chroTABLE IX. DENSITYO F AQLEOI:S SOLUTIONS, :::: C. mate ( I S , ST), and chromium KiCrnOi (52) ( N H M h O : (62) NagCrO4 ( 5 2 , 68) - KzCrOl ( 5 2 , 69) CrOi ( 2 7 , 3 9 . 48,8 7 1 trioxide (6,3 7 ) have been rev by 7 by 910 by 70 hy % by w&ht Density >\.eight Density weight Density xeight Density w&ht Density ported and correlated by the 2.016 1,0140 3.30 10.05 1.0840 1.0190 2.01 1.0173 4.063 1.0306 International Critical Tables. 1.092 5.238 1.2710 11.63 1.0374 J . o o 1.0200 1,0460 29.23 5.05 23.10 1.192 These data have been con7.028 1.0494 8.73 1.325 1.0513 13.03 i.1230 34.02 37.23 1 340 8.440 37.44 1.364 1.0610 10.00 20.51 1.2013 1.0580 firmed and extended, and new 1.5067 8.646 1.0627 1.379 49.98 13.24 1.0801 28.20 1.2890 38.62 10.02 1.0730 17.05 1.1030 32.33 1.339 62.59 1 70R values obtained for the unre17.96 1.1116 36.21 1.389 ported compounds a t 2.5" to 1 434 18.81 1.1169 39.74 21.09 1,1310 30" C. as shown in Table XII. 22.44 1.1400 A slight variation from the International Critical Tables results has been noted in the case of sodium chromate. TABLEX. VAEIATIOKOF DEXSITYWITH TEMPERATURE OVER THE RAXGE VISCOSITY OF SOLUTIOKS. New data obtained for 15.6" TO 50" C. Density a t xasCruO7 KiCrzO7 (iiHa)zCrzOi NazCroOd KzCr04 CrOs the viscosities of the various compounds in water 15. .8 6 Be. ---------Decrease in density per C . X lOs-----solution are present'ed in Table XIII. References 1.036 5 .. 36 .. .. .. .. to previously published data are indicated by ref1.066 9 .. 38" .. 1,074 10 42 , . 36 41 39 erence numbers in the table. 1.133 17 .. .. 48 .. .40. Data are given in International Critical Tables 1.142 18 .. .. 38" .. .. .. 1.160 20 63 .. B- 0_ 45 54 71 55 ( 5 2 )for potassium dichromate, ammonium dichro1.261 30 66 .. .. .. .a,, 1.318 35 .. .. 54 .85. mate, potassium chromate, and chromium trioxide. 1,381 40 76 , . .. 39 The above data confirm and extend the previous 1.436 44 .. 61" 1.526 50 86 .. i124 o3 values, while those presented for sodium chromate 1,706 60 89 .. .. .. .. .. and sodium dichromate dihydrate are new. TABLES 7 I . FREEZIKG POINTSOF S O L ~ T I O XOFS CHROMIUM CHEMIC.4LS
-
7
O
a Saturated solution at l:.6O
C.
ACKNOWLEDGMENT TABLE
20 10 5 2 1 0.5 0.25 0.125 0.063
XI. pH
3 87 100 4.01 50 4.13 20 10 4.33 4.48 5 4.63 2 4.78 1 4 . 9 ~ 5.07
HEXAVALENT CHROXIUM SOLUTIONS AT 25" C.
OF
3.57 3.74 3.91 4.03 4.15 4.31 4.43
300 200 100 50 40 20
3.15 3.27 3.44 3.62 3 66 3.81 10 3 92 5 4.11 4 4.12 2 4.28 1 4.43
6O8 500 401 300 200 100 50 20 10 4.98 2.00 1.00 0,604 o , 201 0.100 0.051 0,020 0.010
CO>lPOUND
9.09 9.10 9.11 9.14 9.20 9.22 9.18 9.11 8.97 8.82 8.62 8.38 8.07 7.80 7.57 7.29 6.92 6.64
400 9 . 8 8 300 9 . 7 7 2 00 9 . 7 2 100 9 . 5 8 40 9.37 20 9 . 2 2 10 9.07 5 8.98 4 8.78 2 8.76 1 8.42
The writer acknowledges with appreciation the aJsistanr-e of members of the Research and Development Department of the Mutual Chemical Company of America, who performed many of the determinations reported in this paper. These workers include D. F. Altimier (now a i t h E. I. du Pont de h'emoursdr Company, Inc.. NiagaraFalls, X.Y.), R.L.Costa,K. A. Lane, C. R. MacLellan, .J. A I . Price, and E. A. Roche. Emma Lee has assisted greatly in checking the numerous literature references. LITERATURE CITED
(1) Alluard, Compt. rend., 59, 500 (1864). (2) Altimier, D. F., J. Am. Chena. Soc., 64, 175 (1942). (3) Amadori, M., Atti accad. naz. Lincei, 21 (51, I, 667 (1912). (4) AM. CHEM.SOC.,Committee on Analytioal Reagents, "Specifi-
cations for Analytical Reagents," Washington, March 1941. (5) Brendler, W., 2. Krist., 58, 445 (1923). (6) Bachner, E. H., and Prins, A , , 2. ghyaik. Chem., 81, 112 (1913). (7) Clarke, F.W., Am. J . S c i . , 14 (a), 2 8 1 (1877).
I N D U S T R I A L A N D E N G I: N E E R I N G C H E M I S T R Y
September 1949
TABLEXII. HEAT CAPACITYOF SOLUTIONS OF CHROMIUM COMPOUNDS AT 25” TO 30” C. NazCrz07.2HzO Heat capacity, %,by weight cal./gram/O C. 10.06 20.47 30.71 40.03 50.51 61.28 70.08
weight
capacity, cal./gram/o c.
0.912 0.832 0.771 0.711 0.647 0.590 0,544
2.42 5.14 11.45
0.962 0.939 0.875
0.949 0,896 0.820 0.767
4.26 18.27 19.10 39.91
20.61 38.05
0,776 0.626
*
1
*
0.941 0.834 0.815 0.715
CrOa
KzCrO4
P
Heat
NazCrO,
( N H4) lCrrO7 5.15 10.79 19.78 27.38
9.28 16.85 24.76 32.05 45.32 58.16
0.895 0.826 0.758 0.705 0.603 0.518
Coppet, M. de, Ann. chim. phys., 25 (4), 502 (1872). Coppet, M. de, 2. physik. Chem., 22, 239 (1897). Donnay, J. D. H., Am. Mineral., 28,313 (1943). Donnay, J. D. H., private communication. Etard, A., A??. chim., 2 (7), 503 (1894). Faasch, H., Uber die Spes. WBrme yon whsserigen LBsungen,” Rostock, 1911. Flach, E., thesis, Leipeig, 1912. Flottman, Fr., Z . anal. Chem., 73, 1 (1928). Gerasimov, Ya. T., Trans. Inst. Pure Chem. Reagents (U.S.S.R.), 6, 22 (1927). Gerasimov, Ya. T., Z . anorg. u. allgem. Chem., 181, 321 (1930); Trans. Inst. Pure Chem. Reagents (U.S.S.R.), 11, 114 (1931). Gossner, B., and Mussgnug, F., 2.Krist., 72,476 (1930). Groschuff, E., 2.anorg. Chem., 58, 102 (1908). Guthrie, F., Phil. Mag., 49 (4), 1 (1875) ; 17 (5), 462 (1884). Ibid., 49, 266 (1875). ENG.CHEM., ANAL.ED., 14, 174 (1942). Hartford, W. H., IND. Hartford, W. H., J . Am. Chem. SOC.,63, 1473 (1941). Hauer, K. R. von, J. prakt. Chem., 83 ( l ) , 359 (1861); 103 (l), 114-20 (1868). Hodgman, C. D., ed., “Handbook of Chemistry and Physics,” 30th ed., Cleveland, Ohio, Chemical Rubber Publishing Co., 1948. Jager, F. M., and Geiins, H. C., 2. anorg. Chem., 119, 145 (1921). Jones, H. C., and Bassett, 1% P., J . Am. Chem. SOC.,34, 334 (1905). Jones, H. C., el al., CarnegieInst. Washington Pub. 60 (1907). Karsten, C. J. B., Schwekgers J. Chem. Physik., 65,394 (1832). Kaufmann, H. J., Lauder, W. B., and Kepner, R. K., IND. ENG. CHEM.,32, 423 (1940). Kohlrsusch, F., Sitz. Akad. Berlin, 1897,90. Koppel, I., and Blumenthal, R., Z . anorg. Chem., 53, 228 (1907). Kremers, P., Ann. Physik, 96, 39 (1855). Kremann, R., Sitzber. Akad. Wiss. W i e n , Muth-naturw., 120, 339 (1911). 1 Lange, ’N. A., “Handbook of Chemistry,” 4th ed., Sandusky, Ohio, Handbook Publishers, 1941. (36) Lehrman, A., Selditch, H., and Skell, P., J . Am. Chem. SOC., 58, 1612 (1936). (37) Marignac, M. C., Arch. sci. phys. et nat., 50 ( 2 ) , 89 (1874); 55 (2), 113 (1876); Ann. chim., 8 (2), 418 (1876). (38) Mellor, J. W., “Comprehensive Treatise on Inorganic and Theoretical Chemistry,” Vol. XI, New York, Longmans, Green & Co., 1931. (39) . . Mendeleef. D. I.. “Etudes des dissolutions aaueuses.” St. Petersburg, 1887. (40) Michel, A., and Krafft, L., Ann. chim., 41 (3), 471 (1854). (41) Miller, J. J., Z . Krist., 94, 131 (1936). (42) Mitscherlich, E., Ann. Physik, 18, 168 (i830). (43) Moissan, H., Compt. rend., 98, 1581 (1884). (44) Moles, E., and Gonsalee, J., A n d e s fts. y qudm. (Madrid), 21, 204 (1923). (45) Moore, H. R., and Blum, W., Bur. Standards J . Research, 5, 255 (1930). (46) Moser, H., “Chemische Abhandling aber des Chrom,” Vienna, 1824. (47) Mtlnzing, L., 2. Krist.,14, 62 (1888). ’
TABLE XIII. VISCOSITIESOF CHROMIUM COMPOUNDS % by
Weight
KaCrzOi
1997
Viscosity, Centipoises 25O C. 40° C. 75’ C.
Viscosity, Centipoises &&t
NazCrz07.2HzO 10.0 20.0 30.0 40.0 45.0 50.0 55.0 60.0 65.0 70.0
0.96 1.08 1.30
1.70
2.00 2.41 3.01 3.94 5.38 8.26
0.70 0.80 0.98 1.24 1.46 1.75 2.15 2.76 3.67 5.23
0.86 0.86 0.90 0.94
.. . .. ,
0.66 0.68 0.72 0.74 0.81
...
0.42 0.50 0.64 0.83 0.97 1.12 1.32 1.60 1.94 2.44
4.78 9.06 14.92 25.0 35.0
0.87 0.89
0.34 0.35 0.39 0.44 0.51 0.69
8.98 16.23 22.96 28.79 34.55 39.12
1.06 1.38 1.88 2.62 3.78 5.54
0.93 1.05 1.20 1.35 1.57 1.64
Q.73 0.84 0.96 1.09 1.25 1.32
75’ C.
0.40 0.48 0.59 0.71 0.85 0.88
17.43 31.33 42.51 51.34 59.21 61.72
... ... ...
0.65 0.68 0.70
.. .. ..
0.35 0.36 0.39 0.48 0.62
NazCrO4 0.85 1.06 1.40 1.88 2.61 3.58
0.42 0.58 0.78 1.08 1.43 1.88
CrOs (66,78)
KzCrO4 ( 7 5 , 74, 80) 9.31 17.51 25.44 31.11 37.48 39.48
40° C.
KzCrzO7
(NHWh07 (73) 5.16 9.76 17.57 23.22 29.6 43.3
25O C.
1.02 1.28 1.73 2.43 3.67 4.36
0.80 1.03 1.34 1.83 2.70 3.12
0.44 0.65 0.89 1.17 1.52 1.65
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