Strong Mineral Acids

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The page below is a sample from the LabCE course Tissue Decalcification for Paraffin Processing. Access the complete course and earn ASCLS P.A.C.E.-approved continuing education credits by subscribing online.

Learn more about Tissue Decalcification for Paraffin Processing (online CE course)
Strong Mineral Acids

Nitric acid formulations and properties:
  • Available as 5% aqueous, 5% alcoholic, 5% nitric in 10% formalin
  • Extremely rapid decalcifier
  • Preserves cartilage and teeth well
  • Slight cellular swelling
  • Overexposure (more than 48 hours) impairs nuclear staining
Hydrochloric acid (HCl) formulations and properties:
  • Available as 0.5N HCl, 8% HCl with 10% formic acid
  • Very rapid and harsh decalcifier
  • High concentration and prolonged exposure damages tissue components and impacts staining
  • CAUTION: HCl and formaldehyde should NEVER be combined in any way
    • Bis-chloromethyl ether forms during chemical reaction (carcinogen)
    • Tissue must be rinsed in water after fixation in formalin prior to decal in HCl. Then, the HCl must be rinsed off in water prior to placing in the tissue processor that uses formalin in processing to avoid chemical reaction and contamination of tissue processor reagents.