what are true and pseudo alums?

what are true and pseudo alums?


1 Answers

AKASH GOYAL AskiitiansExpert-IITD
420 Points
13 years ago

Dear Nikhil

A pseudo alum is a double sulfate of the typical formula ASO4·B2(SO4)3·22H2O, where A is a divalent metal ion, such as cobalt (wupatkiite), manganese (apjohnite), magnesium (pickingerite) or iron (halotrichite or feather alum), and B is a trivalent metal ion. i.e. class of alums in which the usual monovalent metal of a true alum is replaced by a bivalent metal


(MM'(SO4)2 H2O

in which M represents a univalent ion such as K+ and M' represents a trivalent ion such as Al3+.  True alums crystallize in a well-defined octahedron structure and many are beautifully colored, particular those containing d-block elements.


All the best.                                                           


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