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Compositional guideline: Molybdenum trioxide

5 June 2014

Name of the ingredient

Molybdenum trioxide (AAN)

Definition of the ingredient

Molecular formula: MoO3

Molar mass: 143.94

CAS Number: 1313-27-5

Table 1: Ingredient specific requirements
Test Method reference Acceptance criteria
Appearance Visual Yellow-green or grey powder
Loss on drying (dried to a constant weight at 100-105°C)

BP (Appendix IX D)

Not more than 0.5%

BP (General Notices)

Slightly soluble in water. Soluble in concentrated mineral acids, solutions of alkaline hydroxides and ammonia


Ph Eur 2.2.23

Matches spectrum of authenticated reference material

Molybdenum trioxide

Ph Eur 2.2.23

99.5-101.0% (anhydrous basis)
Table 2: Incidental constituents
Test Method reference Acceptance criteria
Incidental metals and non-metals
Heavy metals (as lead)

BP (Appendix VII)

Not more than 10 ppm


Ph Eur 2.4.2

Not more than 10 ppm


Ph Eur 2.4.13

Not more than 200 ppm


Ph Eur 2.4.11

Not more than 5 ppm


BP (Appendix VII)

Not more than 20 ppm

Other organic or inorganic impurities or toxins

Ammonia insoluble matter

(10g sample in 120 mL dilute aqueous ammonia)

Literature method1

Not more than 0.01% w/w
While substance manufacturers are encouraged to include limits for objectionable microorganisms, it is the product into which those substances are formulated that is subject to a legally binding set of criteria. The Therapeutic Goods Order No. 77 'Microbiological Standards for Medicines' mandates that any finished product that contains the ingredient, alone or in combination with other ingredients, must comply with the microbial acceptance criteria set by Clause 9 of the Order.
  1. Reagent Chemicals Ninth Edition, American Chemical Society Specifications

Key to abbreviations

AAS = Atomic Absorption Spectrophotometry

BP = British Pharmacopoeia

Ph Eur = European Pharmacopoeia