Open AccessThe Aqueous Chemistry of Chromium(III) above 100 °C: Hydrothermal Synthesis of Chromium Spinels
Author(s) -
Thomas W. Swaddle,
Joshua Lipton,
Giovanni Guastalla,
Peter A. Bayliss
Publication year - 1971
Publication title -
canadian journal of chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.323
H-Index - 68
eISSN - 1480-3291
pISSN - 0008-4042
DOI - 10.1139/v71-397
Subject(s) - chromium , chemistry , aqueous solution , inorganic chemistry , hydrothermal circulation , perchloric acid , chromate conversion coating , perchlorate , chromite , nuclear chemistry , potassium chromate , chloride , ion , organic chemistry , seismology , geology
The hydrothermal deposition of CrO(OH) from aqueous chromium(III) chloride, nitrate, and perchlorate, and of Cr 3 (SO 4 ) 2 (OH) 5• H 2 O and Cr(OH)SO 4• 2H 2 O(?) from aqueous chromium(III) sulfate, has been investigated. Aqueous chromium(III) is oxidized to chromium(VI) by 0.4 M perchloric acid above 225 °C, and by molecular oxygen above 250 °C. Aqueous chromium(III) can react at 300 °C with iron or steel, cobalt, and copper to produce FeCr 2 O 4 , CoCr 2 O 4 , and Cu 2 Cr 2 O 4 , respectively. CrO(OH) reacts with type 316 stainless steel at 440 °C in supercritical water of density 0.7 g cm −3 to yield (Fe,Ni)-Cr 2 O 4 , which is the "cubic Cr 2 O 3 " of Laubengayer and McCune. The spinels MCr 2 O 4 (M = Mg, Mn, Fe, Co) can be made hydrothermally at ca. 300 °C from Cr(OH) 3 and M(OH) 2 . This information is relevant to corrosion phenomena, and the possible hydrothermal origin of chromite deposits in serpentinized rocks.