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Effect of graphite on molten samarium fluoride at elevated temperatures
J. Inorg. Nucl. Chem., 1960. Vol. 14, pp. 148 to 149. PergamonPress Ltd. Printed in Northern Ireland
LETTERS TO THE EDITOR
Occurrence and separation of higher polythionic acids in Wackenroder liquid (Received 23 February 1960) WE have carried out an investigation of products of the Wackenroder reaction by paper chromatography (Whatman Paper No. l, solvent mixture n-butanol, acetic acid, acetoacetic ester, water, 10:2:1:7 by volume~1~). We find: (I) A small amount of Wackenroder liquid obtained by the reaction of hydrogen sulphide and sulphur dioxide in water yielded nine spots on the paper strips after spraying with silver nitrate solution following the chromatographic separation. By means of; (a) determinations of the R / o f the polythionic acids on samples prepared by established methods;~2.a.4, 5~ (b) determination of x in the formula H~S~Oe, by dissolving the acid from the paper strips in ether and titrating the S2Oa-formed by the decomposition of the acid with C N - a n d SO3--;~5, 6~ and (c) U.V. absorption spectra of the H2S,O6 dissolved from the paper strips by water; it was found that the products formed in the Wackenroder reaction and separated by paper chromatography are H2S40, ( R / = ~0"15, diffuse), HzSsOs (RI = 0'20), H2S6Oe (Ry = 0"25), H2S706 ( R / = 0.30), H2S806 ( R / = 0'37), H2S906 ( R / = 0'45), H2S1006 ( R / = 0"52), H2S~O6 (x > 10, R / = -..-4).65, diffuse), H~S (R~ = 0'90). (2) The polythionic acids formed by the Wackenroder reaction in 50 per cent aqueous CH3COOH are the acids H2S~O6, x = 3-12, in HCI, 2-10 M, the range x = 8-11 is found. The Rt values are recorded above and the acids have been identified by the methods (a), (b), and (c) above. (3) The first products of the Wackenroder reaction are H2SzO3 and HzSsOe. (4) The higher polythionic acids (above hexathionic) undergo decomposition on adding potassium acetate to Wackenroder liquid; as is observed in the POLLARD solvent, tT~ This is in accordance with the sensitivity of the polythionic acids to hydroxyl ions. tS~ The results of these experiments clearly demonstrate the occurrence of higher polythionic acids in the Wackenroder liquid, the influence of acidity on the reaction, and the possibility of preparation for the first time of pure H~S~O6 with x = 9 and 11. The only reaction mechanism which agrees with these results as well as with unpublished radiochemical investigation is the one proposed by VAN DER HEUDE,t°~ with the assumption that the chainlength in the intermediate is increasing with the acidity. Institute o f General Chemistry University o f Padua
R. BARBIERI M. BRUNO
~1~E. SCOFFONEand E. CAmNL Ric. Sci. 7, 2109 (1955). ~ H. S'rA~, M. GoEnmNo and U. FELDMANN,Z. Anorg. Chem. 250, 226 (1942). ts~ M. GOEHmNC and U. FELDMANN,Z. Anorg. Chem. 257, 223 (1948). t4~ E. WEITZ and F. ACHTE~ERO, Ber. 61, 399 (1928). ts~ M. SCHMIDT,Z. Anorg. Chem. 289, 158 (1957). tal A. KURTENACKERand E. GOLDBACH,Z. Anorg. Chem. 166, 177 (1927). 17~F. H. POLLARD, J. F. W. McOMIE and D. J. JONES,J. Chem. Soc. 4337 (1955). ~s~A. KURTENACKER,A. MUTSCHINand F. STASTNY,Z. Anorg. Chem. 229, 19 (1936). la~ H. B. VAN DER HEI~DE, Contribution to the Chemistry of the Inorganic Acids of Sulphur. University of Amsterdam, Holland (1955); and reported bibliography.
Effect of graphite on molten samarium fluoride at elevated temperatures ~1~ (Received 16 March 1960) THE densities of the Group IIA and IIIA fluorides in the molten state were determined by heating these fluorides in a graphite crucible to temperatures above their melting points (1600-2500°K) and c~ This work was financed by the National Science Foundation, Research Grant NSF-G6278. 148
Letters to the editor
149
measuring the loss in weight of an immersed tungsten or molybdenum sinker, c2,8,4~ Of the fluorides studied (barium, strontium, calcium, magnesium, yttrium, lanthanum, cerium, praeseodymium, neodymium and samarium fluorides) it was found that only the neodymium and samarium fluorides reacted with the graphite. When molten neodymium fluoride, NdFs, was heated for 2 hr in a graphite crucible at a temperature ranging from 1700 ° to 2200°K, about 1.5 per cent of the fluoride was converted into the carbide. None of the other fluorides formed more than 0.1 per cent even when heated to 25O0°K. When samarium trifluoride, a white solid melting at about 1670°K was heated in a graphite crucible, it was reduced to the red-brown difluoride as follows: 4 SmF3 + C ---* 4 SmF~ + CF4 (or higher carbon fluorides). None of the other fluorides were reduced by the graphite. The effects of temperature, time and carbon surface area on percent reduction of SmF3 to SmF3 were studied. The conditions used and results obtained are tabulated in Table I and show that increases in heating time, temperature and carbon TABLE 1.--REDUCTION OF SmFa TO S mF s BY GRAPHITE
Condition
Graphite surface area, (cm2/g SmF3)
I Wt. SmFs (g)
Temperature (°K)
Time (hr)
1600-1800 1800-2200 2200-2300
1
1700-2000 2000-2200
1
1~
16.5
1550 1550-1700 1700-2110
1 1
11.4
2 1 t 4
;raphite crucible and tungsten float
0"35
350
3raphite crucible only
0"40
30
3raphite crucible and 2 g graphite powder
lo0
3raphite crucible and graphite rods
1"2
100
1600-2080 2080-2300 2300-2380
3raphite crucible and graphite chips
3"9
116
2175-2250
1½ 1
Reduction (wt. ~ )
6.8
24.8
30"3
surface area all tend to increase the percent reduction. The maximum reduction obtained to date is 30 wt. ~o. The effects of metals, such as molybdenum and tungsten, on the reduction of the trivalent to the divalent samarium fluoride was studied. It was found that when 100 g of SmFn was melted and heated at 2000 ! 25°K for 1-2 hr in a molybdenum crucible (surface area = 50 cm ~) with tungsten wires (surface area = 40 cm ~) inserted into the melt, less than 0.3 wt. ~ of the trifluoride was reduced to the difluoride. Therefore tungsten and molybdenum under these conditions have little effect on the reduction of SmF3 to SmF2. A. D. KIRSHENBAUM Research Institute of Temple University J . A . CAHILL 4150 Henry Avenue Philadelphia 44, Pennsylvania (~ A. D. KmSttENBAUMand J. A. C^mLL, Technical Note No. 9, Research Institute of Temple University, Contract No. AF 18(600)-1475 (1959). iz) A. D. KIRSHENBAUM,First Annual Report on High Temperature Inorganic Chemistry. National Science Foundation, Research Grant NSF-G6278, Research Institute of Temple University (1959). (*~ A. D. KIRSHENBAUM,J. A. CAHILL and C. S. STOKES,J. Inorg. Nucl. Chem. In press (1960).
LETTERS TO THE EDITOR
Occurrence and separation of higher polythionic acids in Wackenroder liquid (Received 23 February 1960) WE have carried out an investigation of products of the Wackenroder reaction by paper chromatography (Whatman Paper No. l, solvent mixture n-butanol, acetic acid, acetoacetic ester, water, 10:2:1:7 by volume~1~). We find: (I) A small amount of Wackenroder liquid obtained by the reaction of hydrogen sulphide and sulphur dioxide in water yielded nine spots on the paper strips after spraying with silver nitrate solution following the chromatographic separation. By means of; (a) determinations of the R / o f the polythionic acids on samples prepared by established methods;~2.a.4, 5~ (b) determination of x in the formula H~S~Oe, by dissolving the acid from the paper strips in ether and titrating the S2Oa-formed by the decomposition of the acid with C N - a n d SO3--;~5, 6~ and (c) U.V. absorption spectra of the H2S,O6 dissolved from the paper strips by water; it was found that the products formed in the Wackenroder reaction and separated by paper chromatography are H2S40, ( R / = ~0"15, diffuse), HzSsOs (RI = 0'20), H2S6Oe (Ry = 0"25), H2S706 ( R / = 0.30), H2S806 ( R / = 0'37), H2S906 ( R / = 0'45), H2S1006 ( R / = 0"52), H2S~O6 (x > 10, R / = -..-4).65, diffuse), H~S (R~ = 0'90). (2) The polythionic acids formed by the Wackenroder reaction in 50 per cent aqueous CH3COOH are the acids H2S~O6, x = 3-12, in HCI, 2-10 M, the range x = 8-11 is found. The Rt values are recorded above and the acids have been identified by the methods (a), (b), and (c) above. (3) The first products of the Wackenroder reaction are H2SzO3 and HzSsOe. (4) The higher polythionic acids (above hexathionic) undergo decomposition on adding potassium acetate to Wackenroder liquid; as is observed in the POLLARD solvent, tT~ This is in accordance with the sensitivity of the polythionic acids to hydroxyl ions. tS~ The results of these experiments clearly demonstrate the occurrence of higher polythionic acids in the Wackenroder liquid, the influence of acidity on the reaction, and the possibility of preparation for the first time of pure H~S~O6 with x = 9 and 11. The only reaction mechanism which agrees with these results as well as with unpublished radiochemical investigation is the one proposed by VAN DER HEUDE,t°~ with the assumption that the chainlength in the intermediate is increasing with the acidity. Institute o f General Chemistry University o f Padua
R. BARBIERI M. BRUNO
~1~E. SCOFFONEand E. CAmNL Ric. Sci. 7, 2109 (1955). ~ H. S'rA~, M. GoEnmNo and U. FELDMANN,Z. Anorg. Chem. 250, 226 (1942). ts~ M. GOEHmNC and U. FELDMANN,Z. Anorg. Chem. 257, 223 (1948). t4~ E. WEITZ and F. ACHTE~ERO, Ber. 61, 399 (1928). ts~ M. SCHMIDT,Z. Anorg. Chem. 289, 158 (1957). tal A. KURTENACKERand E. GOLDBACH,Z. Anorg. Chem. 166, 177 (1927). 17~F. H. POLLARD, J. F. W. McOMIE and D. J. JONES,J. Chem. Soc. 4337 (1955). ~s~A. KURTENACKER,A. MUTSCHINand F. STASTNY,Z. Anorg. Chem. 229, 19 (1936). la~ H. B. VAN DER HEI~DE, Contribution to the Chemistry of the Inorganic Acids of Sulphur. University of Amsterdam, Holland (1955); and reported bibliography.
Effect of graphite on molten samarium fluoride at elevated temperatures ~1~ (Received 16 March 1960) THE densities of the Group IIA and IIIA fluorides in the molten state were determined by heating these fluorides in a graphite crucible to temperatures above their melting points (1600-2500°K) and c~ This work was financed by the National Science Foundation, Research Grant NSF-G6278. 148
Letters to the editor
149
measuring the loss in weight of an immersed tungsten or molybdenum sinker, c2,8,4~ Of the fluorides studied (barium, strontium, calcium, magnesium, yttrium, lanthanum, cerium, praeseodymium, neodymium and samarium fluorides) it was found that only the neodymium and samarium fluorides reacted with the graphite. When molten neodymium fluoride, NdFs, was heated for 2 hr in a graphite crucible at a temperature ranging from 1700 ° to 2200°K, about 1.5 per cent of the fluoride was converted into the carbide. None of the other fluorides formed more than 0.1 per cent even when heated to 25O0°K. When samarium trifluoride, a white solid melting at about 1670°K was heated in a graphite crucible, it was reduced to the red-brown difluoride as follows: 4 SmF3 + C ---* 4 SmF~ + CF4 (or higher carbon fluorides). None of the other fluorides were reduced by the graphite. The effects of temperature, time and carbon surface area on percent reduction of SmF3 to SmF3 were studied. The conditions used and results obtained are tabulated in Table I and show that increases in heating time, temperature and carbon TABLE 1.--REDUCTION OF SmFa TO S mF s BY GRAPHITE
Condition
Graphite surface area, (cm2/g SmF3)
I Wt. SmFs (g)
Temperature (°K)
Time (hr)
1600-1800 1800-2200 2200-2300
1
1700-2000 2000-2200
1
1~
16.5
1550 1550-1700 1700-2110
1 1
11.4
2 1 t 4
;raphite crucible and tungsten float
0"35
350
3raphite crucible only
0"40
30
3raphite crucible and 2 g graphite powder
lo0
3raphite crucible and graphite rods
1"2
100
1600-2080 2080-2300 2300-2380
3raphite crucible and graphite chips
3"9
116
2175-2250
1½ 1
Reduction (wt. ~ )
6.8
24.8
30"3
surface area all tend to increase the percent reduction. The maximum reduction obtained to date is 30 wt. ~o. The effects of metals, such as molybdenum and tungsten, on the reduction of the trivalent to the divalent samarium fluoride was studied. It was found that when 100 g of SmFn was melted and heated at 2000 ! 25°K for 1-2 hr in a molybdenum crucible (surface area = 50 cm ~) with tungsten wires (surface area = 40 cm ~) inserted into the melt, less than 0.3 wt. ~ of the trifluoride was reduced to the difluoride. Therefore tungsten and molybdenum under these conditions have little effect on the reduction of SmF3 to SmF2. A. D. KIRSHENBAUM Research Institute of Temple University J . A . CAHILL 4150 Henry Avenue Philadelphia 44, Pennsylvania (~ A. D. KmSttENBAUMand J. A. C^mLL, Technical Note No. 9, Research Institute of Temple University, Contract No. AF 18(600)-1475 (1959). iz) A. D. KIRSHENBAUM,First Annual Report on High Temperature Inorganic Chemistry. National Science Foundation, Research Grant NSF-G6278, Research Institute of Temple University (1959). (*~ A. D. KIRSHENBAUM,J. A. CAHILL and C. S. STOKES,J. Inorg. Nucl. Chem. In press (1960).