Heller and Paul double oxalate is also known as:

Heller and Paul double oxalate is a combination of ammonium and potassium oxalate. It is an anticoagulant that is used commonly for hematological analyses. It does not cause shrinkage or enlargement of red blood cells. Ammonium oxalate cannot be used when test for urea are carried out. Ref: Diagnosis of Hemophilia and Bleeding Disorders, 2nd Edition, Page 11