Formaldehyde is a gas at room temperature and one atmosphere of pressure. Our product (catalog # 120B) is a saturated solution of formaldehyde in water and has a concentration of 37% w/w formaldehyde. This solution is properly called “formalin.” It is intended for use as a general laboratory reagent and contains about 10% methanol to prevent polymerization. It should not be confused with formalin 1:10 which is a 1:10 dilution of formalin but is also buffered to a pH of 7.0.