IRISH MOSS or CARRAGEEN (Irish carraigeen, "moss of the rock"), a seaweed (Chondrus crispus) which grows abundantly along the rocky parts of the Atlantic coast of Europe and North America. In its fresh condition the plant is soft and cartilaginous, varying in colour from a greenish-yellow to a dark purple or purplish-brown ; but when washed and sun-dried for preservation it has a yellowish translucent horn-like aspect and consistency. The principal constituent of Irish moss is a muci laginous body, of which it contains about 55%; and with that it has nearly 0% of nitrogenous material and about 5% of mineral matter rich in iodine and sulphur. When softened in water it has
a sea-like odour, and from the abundance of its mucilage it will form a jelly on boiling with from 20 to 3o times its weight of water. The jelly thus formed of Irish moss is used as food. It may also be used as a thickener in calico-printing and for fining beer.