Final answer:
EDTA is the anticoagulant commonly used in blood film studies to prevent coagulation by binding calcium ions.
Step-by-step explanation:
The anticoagulant used for most blood film studies is EDTA (Ethylenediaminetetraacetic acid). EDTA works by binding to the calcium ions in blood, which are necessary for blood coagulation, thereby preventing clot formation. This anticoagulant is preferred for hematological studies because it preserves the shape of blood cells, which is critical for accurate microscopy.