Cellulose diacetate, sometimes called diacetate, is a synthetic polymer made by treating cellulose with acetic acid. It consists of two acetate radicals on each unit of D-anhydroglucopyranose of the cellulose molecule. It was first developed in the United States. It is distinguished from cellulose acetate and cellulose triacetate. It is fragile since it is based on cellulose. When cellulose diacetate deteriorates, it shrinks and releases acetic acid, causing a "vinegar syndrome". A cellulose diacetate film is also called a safety film. The cellulose diacetate is biodegradable and hydrophilic.