Formaldehyde is the simplest member of the aldehyde group and its chemical formula is HCHO. Formaldehyde, although gaseous at room temperature, dissolves well in water.
Formaldehyde is usually marketed as a 37% aqueous solution called formalin. Formaldehyde in polymerized water contains small bonded HCHO monomers. Formalin usually contains a small percentage of methanol to limit polymerization. Formaldehyde has the same properties as other aldehydes.