Stability of reduced molybdosilicic acids.
The effect of reduction on the stability of molybdosilicic acids (MSA) has been investigated. It has been found that when two or more of the 12 Mo(VI) atoms in alpha or beta-MSA are reduced to Mo(V), the products are stable in alkaline medium. Also, beta-MSA reduced to this extent is stable at higher temperature and is not transformed into alpha-MSA. Solutions in which the apparent degree of reduction is less than 2 Mo(V) per MSA ion should be treated as a mixture of unreduced MSA and MSA reduced exactly to 2 Mo(V) per MSA ion. A mixture of unreduced MSA and MSA reduced to contain 4 Mo(V) per MSA ion is not a stable system. The yellow unreduced MSA is reduced by the reduced form to give the product with 2 Mo(V) per MSA ion. The consequences for determining silicon as MSA are given, as well as a method of obtaining pure beta-MSA from a mixture of alpha-MSA and beta-MSA.
Migdalski
J
J
Academy of Mining and Metallurgy in Kraków, Institute of Materials Science, Al. Mickiewicza 30, 30-059 Kraków, Poland.
Kowalski
Z
Z