PGA can also be obtained by reacting carbon monoxide, formaldehyde or one of its related compounds like paraformaldehyde or trioxane, in presence of an acidic catalyst. In a carbon monoxide atmosphere an autoclave is loaded with the catalyst (chlorosulfonic acid), dichloromethane and trioxane, then it is charged with carbon monoxide until a specific pressure is reached; the reaction is stirred and allowed to proceed at a temperature of about 180 °C for two hours. Upon completion the unreacted carbon monoxide is discharged and a mixture of low and high MW polyglycolide is collected.[8]