Chemistry Explained: Molybdenum, Molybdate

Document ID

Document ID TE12988

Published Date

Published Date 05/12/2022
Chemistry Explained: Molybdenum, Molybdate
Explanation of the reactions and methods for the parameter Molybdenum, Molybdate.


Molybdenum (molybdate) salts are commonly used as corrosion inhibitors in cooling water systems. There are numerous procedures for determining molybdenum as molybdate (MoO4 2–) in water. The Mercaptoacetic Acid Method is one of the most frequently referenced methods for determining molybdenum. The Hach procedure improves and simplifies this time-proven procedure.

Chemical Reactions:

Mercaptoacetic acid

The MolyVer™ (Mercaptoacetic Acid) Method utilizes three reagent powders. First, a MolyVer 1 Reagent Powder Pillow is added. MolyVer 1 contains a buffer to control the pH, in addition to a chelating agent to mask interferences.

Low test results can be caused from reduction of Mo6+ to Mo5+, because the test is specific for Mo6+. MolyVer 2 Reagent Powder is added to prevent reduction of the Mo6+ ion. Finally, mercaptoacetic acid, contained in MolyVer 3 Reagent Powder, is added. The reaction of MolyVer 3 with Mo6+ results in formation of a characteristic yellow color. Development of the yellow color follows Beer’s Law over the range of the test.

This information is from the document Molybdenum, Molybdate for Water

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