title: Identification of calcium oxalate crystals using alizarin red S stain.
abstract: Calcium oxalate crystals stain with alizarin red S at a pH of 7.0 but not at a pH of 4.2. In contrast, calcium phosphate and calcium carbonate stain at a pH of both 7.0 and 4.2. This difference allows presumptive identification of calcium oxalate deposits. The identity of calcium oxalate can then be confirmed by its insolubility in 2M acetic acid, since both calcium carbonate and calcium phosphate are soluble. We have applied this procedure for several years and have found it to be a rapid, reliable, and technically simple procedure for distinguishing calcium oxalate from other calcium deposits.
authors.forename: A D
authors.initials: AD
authors.lastname: Proia
authors.forename: N T
authors.initials: NT
authors.lastname: Brinn
mesh_terms: D000818:Animals; D000880:Anthraquinones; D002119:Calcium Carbonate / Q000032:analysis; D002129:Calcium Oxalate / Q000032:analysis*; D002130:Calcium Phosphates / Q000032:analysis; D019855:Ethylene Glycol; D005026:Ethylene Glycols / Q000506:poisoning; D006651:Histocytochemistry; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007668:Kidney / Q000032:analysis; D007676:Kidney Failure, Chronic / Q000378:metabolism; D010070:Oxalates / Q000652:urine; D019815:Oxalic Acid; D051381:Rats; D011919:Rats, Inbred Strains; D012995:Solubility; D013194:Staining and Labeling
chemical_list: D000880:Anthraquinones; D002130:Calcium Phosphates; D005026:Ethylene Glycols; D010070:Oxalates; C485828:alpha-tricalcium phosphate; C485830:tetracalcium phosphate; D002129:Calcium Oxalate; C004468:Alizarin Red S; C485838:calcium phosphate, monobasic, anhydrous; C020243:calcium phosphate; D019815:Oxalic Acid; D019855:Ethylene Glycol; D002119:Calcium Carbonate; C485829:calcium phosphate, dibasic, anhydrous