Carrageenan is obtained by aqueous extraction of natural strains of seaweeds of Gigartinaceae, Solieriaceae, Hypneaceae and Furcellar iaceae, families of the class Rhodophyceae (red seaweeds). No organic precipitant shall be used other than methanol, ethanol and propane-2-ol. Carrageenan consists chiefly of potassium, sodium, magnesium and calcium salts of polysaccharide sulphate esters which, on hydrolysis, yield galactose and 3,6-anhydrogalactose. Carrageenan shall not be hydrolysed otherwise chemically degraded.