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The influence of chromium chloride on the hydrolysis of pyrophosphate
I 172
Letters to the editor
manner, from the experimental vapour pressure data of Na '~' we obtain at 2100°K a v.p. or Perqt. = 120 arm. Thus, NovlKov's 120.90.2 Z~ - - 0-06,: 82.06.2100 far below our value = 0'29; van der Waals' equation itself requires a Z~ of = 0"37v Novmov's Petit. and Vertt. are therefore also too low! The same arguments apply to K and Cs. This discussion emphasises the desirability of determining the critical parameters of the alkali metals; the easiest to obtain experimentally should be those of caesium, since it has the lowest Ter, t. and Petit. of the alkali metals, ~s~that is 2150°K and 160 arm. Research Institute of Temple University 4150, Henry Avenue Philadelphia, Pa., U.S.A.
A. V. GROSSE
~J M. S r r n o "Sodium, its manufacture, properties and uses", A.C.S. monograph No. 133, Reinhold, Table A-9, pages 478--486. New York (1956).
J. Inorg. Nucl. Chem.. 1965. Vol. 27. pp. 1172 to 1173. Pergamon Pr¢~ Ltd. Printed in Northern ireland
T h e influence o f c h r o m i u m chloride on the
hydrolysis of
pyrophosphate
(Received 10 November 1964) IN A RECENT publication RAINEY et al. ct~ measured the rate of hydrolysis of 0.05 M pyrophosphate in 0-2 M hydrochloric acid solutions containing varying quantities of chromium chloride, [Cr(HsO),CI~]CI2HtO. It is claimed that 0.025 moles of chromium chloride will completely stop the acidic hydrolysis of pyrophosphate. These authors based their conclusion on electrical conductivity measurements. it is my contention that electrical conductivity measurements do not yield reliable phosphate hydrolysis data. Moreover, since the work of RnlNEV et al. is not in general agreement with data previously obtained in our laboratory, ~'sj the rate of hydrolysis of pyrophosphat¢ was measured by direct analysis when the pyrophosphate was subjected to the conditions stipulated by R~INEY et al. A solution was prepared which contained 0-05 moles of Na4PtO~ and 0.025 moles of CrCls.6HtO in 1 I. of 0.2 M hydrochloric acid. The solution was placed in a thermostat at 60.0°C. This is 10°C lower than the thermostat employed by RAINEY et al. The solution was analysed at time intervals of 4 hr 50 rain, 9 hr 30 min and 78 hr as well as at zero time. A paper chromatographic method was used to analyse the phosphate solution. Since C # + interferes with the analysis, it was necessary to remove this cation before the solution could be analysed. It was learned that the easiest way to rid the analysis of C#* interference was to oxidize the Cr *+ to C r O c with hydrogen peroxide. The following scheme was employed. Twenty-five milliliters of the phosphate solution was made basic with sodium carbonate (pH 10) and 10 ml of 3 % hydrogen peroxide was added to the solution. The solution was heated to a boil for about 2 min and was then allowed to stand for 15 min. This not only oxidizes the C#* to C r O c but also rids the solution of excess peroxide. The cooled solution was adjusted to pH 7 with hydrochloric acid and the phosphate was analysed by paper chromatography using a method similar to that recommended by CROW'rHER.~' The C r O c does not interfere in this analysis but is found as a well separated band which may be easily identified and removed if desired. ctJ j. M. RAI~m¥, M. M. JoNEs and W. L. L o c ~ x n T , J. lnorg. Nucl. Chem. 26, 1415 (1964). c,~ j. R. V^N WAZER, E. J. GmvVrrH and J. F. McCuLLOUGH, J. Amer. Chem. Soc. 77, 287 0955). ca~ E. J. GRIFFITH, lndustr. Engng. Chem. 51,240 (1959). t,~ j. CROWTHER, Analyt. Chem. 26, 1383 (1954).
Lettet~ to the editor
I 173
The analysis showed that at zero time the sample contained only pyrophmphate. After 4 hr 50 min there was a strong concentration of orthophmphate and after 78 hr only traces of the pyrophmphate remained. A semi-quantitative analysis of the chromatographs showed that the half-life of the pyrophmphate was approximately 7-5 hr. This half-life is in reasonably good agreement with the values previously reported from this laboratory. I cannot agree with R ~ n , et aL that C P + completely stops the hydrolysis of pyrophosphate. Our data indicate that Cr *+ has only a small influence and that this influence is to increase the rate of hydrolysis of pyrophosphate in acidic media. E. J. GatFmH
Inorganic Chemicals Division Monsanto Company St. Louis, Missouri 63166
J. Inors. Nucl. Chem., 1965. Vol. 27. pp. 1173 to 117,1. Persamon Preu Lt0. Printed in Northern Ire,llmd
Crystal structure of zirconium tetraboride*
(Received 21 January 1965) AMIIETHAILINGAMand MURALIDHARANell recently reported unit cell parameters and X-ray powder pattern data for a material they describe as fl-ZrF,. This material appears to be identical with the TABLE I . - - X - R A Y
POWDER DATA
t/to
d(A)
l*
d(A)*
15 25 5 20
6'88 6.09 4.97 4.77
w vw
6.87 6.06
vw
4"75
100
3"88
s
3.88
1"21, 21 i
i0 100
3'85 3.65
3.63
002 211
m
hk/ 110 Ol 1 020 ~, 200
100 3.44 vs 3"43 TI2, 220 50 3-28 m 3.27 112 30 3"12 m 3.09 130, 202 50 3-03 vs 3-01 022, 03 I, 3 I0 5 2"58 vvw 2.57 321 5 2-49 013, 222 5 2-472 312 5 2'385 vvw 2'37 400 5 2.307 T41 5 2'176 411 5 2-140 213 5 2'029 033 5 2'021 'J32 25 1"961 v, i'95 402 Monoclinic space group 12/c (BURBANK and BENSEk') 'Q' ao -- 9'57 A, b, = 9"93 A, co = 7"73 A, fl = 99"47 °, Z := 12, density = 4.549 Monoclinic space group C2/c (W. H. ZACHAaIAStN)cj~ a, - I 1.69 A, be ~ 9-87 A, Co = 7.64 A,/~ -= 126-15 ° * AMIRTHALINGAM a n d MURALIDHARAN'S
data.
,1~ V. AMIRTHALINGAM a n d K . V. MURALIDHARAN, J . lnorl~'. N u c l . C h e m . 26, 2 0 3 8
(1964).
Letters to the editor
manner, from the experimental vapour pressure data of Na '~' we obtain at 2100°K a v.p. or Perqt. = 120 arm. Thus, NovlKov's 120.90.2 Z~ - - 0-06,: 82.06.2100 far below our value = 0'29; van der Waals' equation itself requires a Z~ of = 0"37v Novmov's Petit. and Vertt. are therefore also too low! The same arguments apply to K and Cs. This discussion emphasises the desirability of determining the critical parameters of the alkali metals; the easiest to obtain experimentally should be those of caesium, since it has the lowest Ter, t. and Petit. of the alkali metals, ~s~that is 2150°K and 160 arm. Research Institute of Temple University 4150, Henry Avenue Philadelphia, Pa., U.S.A.
A. V. GROSSE
~J M. S r r n o "Sodium, its manufacture, properties and uses", A.C.S. monograph No. 133, Reinhold, Table A-9, pages 478--486. New York (1956).
J. Inorg. Nucl. Chem.. 1965. Vol. 27. pp. 1172 to 1173. Pergamon Pr¢~ Ltd. Printed in Northern ireland
T h e influence o f c h r o m i u m chloride on the
hydrolysis of
pyrophosphate
(Received 10 November 1964) IN A RECENT publication RAINEY et al. ct~ measured the rate of hydrolysis of 0.05 M pyrophosphate in 0-2 M hydrochloric acid solutions containing varying quantities of chromium chloride, [Cr(HsO),CI~]CI2HtO. It is claimed that 0.025 moles of chromium chloride will completely stop the acidic hydrolysis of pyrophosphate. These authors based their conclusion on electrical conductivity measurements. it is my contention that electrical conductivity measurements do not yield reliable phosphate hydrolysis data. Moreover, since the work of RnlNEV et al. is not in general agreement with data previously obtained in our laboratory, ~'sj the rate of hydrolysis of pyrophosphat¢ was measured by direct analysis when the pyrophosphate was subjected to the conditions stipulated by R~INEY et al. A solution was prepared which contained 0-05 moles of Na4PtO~ and 0.025 moles of CrCls.6HtO in 1 I. of 0.2 M hydrochloric acid. The solution was placed in a thermostat at 60.0°C. This is 10°C lower than the thermostat employed by RAINEY et al. The solution was analysed at time intervals of 4 hr 50 rain, 9 hr 30 min and 78 hr as well as at zero time. A paper chromatographic method was used to analyse the phosphate solution. Since C # + interferes with the analysis, it was necessary to remove this cation before the solution could be analysed. It was learned that the easiest way to rid the analysis of C#* interference was to oxidize the Cr *+ to C r O c with hydrogen peroxide. The following scheme was employed. Twenty-five milliliters of the phosphate solution was made basic with sodium carbonate (pH 10) and 10 ml of 3 % hydrogen peroxide was added to the solution. The solution was heated to a boil for about 2 min and was then allowed to stand for 15 min. This not only oxidizes the C#* to C r O c but also rids the solution of excess peroxide. The cooled solution was adjusted to pH 7 with hydrochloric acid and the phosphate was analysed by paper chromatography using a method similar to that recommended by CROW'rHER.~' The C r O c does not interfere in this analysis but is found as a well separated band which may be easily identified and removed if desired. ctJ j. M. RAI~m¥, M. M. JoNEs and W. L. L o c ~ x n T , J. lnorg. Nucl. Chem. 26, 1415 (1964). c,~ j. R. V^N WAZER, E. J. GmvVrrH and J. F. McCuLLOUGH, J. Amer. Chem. Soc. 77, 287 0955). ca~ E. J. GRIFFITH, lndustr. Engng. Chem. 51,240 (1959). t,~ j. CROWTHER, Analyt. Chem. 26, 1383 (1954).
Lettet~ to the editor
I 173
The analysis showed that at zero time the sample contained only pyrophmphate. After 4 hr 50 min there was a strong concentration of orthophmphate and after 78 hr only traces of the pyrophmphate remained. A semi-quantitative analysis of the chromatographs showed that the half-life of the pyrophmphate was approximately 7-5 hr. This half-life is in reasonably good agreement with the values previously reported from this laboratory. I cannot agree with R ~ n , et aL that C P + completely stops the hydrolysis of pyrophosphate. Our data indicate that Cr *+ has only a small influence and that this influence is to increase the rate of hydrolysis of pyrophosphate in acidic media. E. J. GatFmH
Inorganic Chemicals Division Monsanto Company St. Louis, Missouri 63166
J. Inors. Nucl. Chem., 1965. Vol. 27. pp. 1173 to 117,1. Persamon Preu Lt0. Printed in Northern Ire,llmd
Crystal structure of zirconium tetraboride*
(Received 21 January 1965) AMIIETHAILINGAMand MURALIDHARANell recently reported unit cell parameters and X-ray powder pattern data for a material they describe as fl-ZrF,. This material appears to be identical with the TABLE I . - - X - R A Y
POWDER DATA
t/to
d(A)
l*
d(A)*
15 25 5 20
6'88 6.09 4.97 4.77
w vw
6.87 6.06
vw
4"75
100
3"88
s
3.88
1"21, 21 i
i0 100
3'85 3.65
3.63
002 211
m
hk/ 110 Ol 1 020 ~, 200
100 3.44 vs 3"43 TI2, 220 50 3-28 m 3.27 112 30 3"12 m 3.09 130, 202 50 3-03 vs 3-01 022, 03 I, 3 I0 5 2"58 vvw 2.57 321 5 2-49 013, 222 5 2-472 312 5 2'385 vvw 2'37 400 5 2.307 T41 5 2'176 411 5 2-140 213 5 2'029 033 5 2'021 'J32 25 1"961 v, i'95 402 Monoclinic space group 12/c (BURBANK and BENSEk') 'Q' ao -- 9'57 A, b, = 9"93 A, co = 7"73 A, fl = 99"47 °, Z := 12, density = 4.549 Monoclinic space group C2/c (W. H. ZACHAaIAStN)cj~ a, - I 1.69 A, be ~ 9-87 A, Co = 7.64 A,/~ -= 126-15 ° * AMIRTHALINGAM a n d MURALIDHARAN'S
data.
,1~ V. AMIRTHALINGAM a n d K . V. MURALIDHARAN, J . lnorl~'. N u c l . C h e m . 26, 2 0 3 8
(1964).