Dibutyl Squarate or SADBE
Dibutyl squarate or squaric acid dibutyl ester (FR-0553) is an oily ester of squaric acid that has found use in the treatment of skin warts and alopecia (hair loss). Frinton Laboratories, Inc. offers this in small to medium quantities, from grams to kilograms. It appears as a clear, oily liquid and with a purity higher than 98%. The parent acid, squaric acid, also called quadratic acid, despite its name is not a perfect square since the carbon-carbon bonds are not equal all around.
Dibutyl squarate (SADBE) is stable for a period of at least 3 years when kept sealed and at ambient temperature, as indicated by the absence of hydrolysis products and the unaltered HPLC trace. When hydrolysis occurs, a fine white solid appears. This is squaric acid. No other solids develop. Keep SADBE in a cool, dry environment. A few, brief openings of the bottle for transfers, will not generally affect the product, unless the atmosphere is heavily laden with moisture, such as in the tropics. In high humidity areas and for long term storage it would be best to keep dibutyl squarate in a cold, dry atmosphere as found in a refrigerator. When one needs to transfer a measured amount, let the liquid come to room temperature, and open in a dry box or at least in an air conditioned (not humid) room.