Epitochem

Zinc stearate

Zinc stearate

Zinc stearate is a fine, white, hydrophobic powder derived from stearic and palmitic acids. It is odorless or has a faint characteristic smell and is free from grittiness. It is insoluble in water, ethanol, and ether, but soluble in aromatic solvents and acids. Zinc stearate is primarily used as a lubricant in solid dosage forms and is also found in creams, ointments, and dusting powders. Its softening and melting range is 120–122 °C.

Chemical Name and CAS Registry Number :-Octadecanoic acid calcium salt [557-05-1]
Functional Category :-Tablet and capsule lubricant

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Pharmacopeial Specifications

Test PhEur 2005 USP 28
Identification ✔ ✔
Acid value 195–210 —
Assay (Zn / ZnO) 10.0–12.0% Zn 12.5–14.0% ZnO
Heavy metals (Pb, Cd) ≤25 ppm, ≤5 ppm ≤0.001% (Pb)
Organic volatile impurities — ✔

Applications in Pharmaceutical Formulation or Technology

Zinc stearate is used in concentrations of 0.5–1.5% as a lubricant in tablet and capsule production. It is also employed as a thickening and opacifying agent in creams and ointments and was once used in baby powders (now discontinued due to inhalation risks).

Comment

Zinc stearate, though effective as a lubricant, must be handled with care to avoid inhalation. It shares functional and chemical characteristics with magnesium and calcium stearates. The EINECS number is 209-151-9.

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