4326. Iodine

4326.      Iodine. A chemical element found both in the animal, vegetable, and mineral kingdoms, but exists in greatest abundance in sea-weed. It is principally manufactured from the mother-waters of kelp. Iodine is usually met with under the form of semi-crystalline lumps, having a metallic lustre, or friable scales, somewhat resembling gunpowder. It has a greyish-black color, a ] hot, acrid taste, and a disagreeable odor not much unlike that of chlorine. It fuses at 225° Fahr., volatilizes slowly at ordinary temperatures, boils at 347°, and when mixed with water rapidly rises along with its vapor at 212°. It dissolves in 7000 parts of water, and freely in alcohol and ether. It may be crystallized in large rhomboidal plates, by exposing to the air a solution of it in hydriodic acid. Iodine, like chlorine, has an extensive range of affinity; with the salifiable bases it forms compounds termed iodides, iodUrets, or hY-driodates ; and it destroys vegetable colors.

4327. To Obtain Iodine

4327. To Obtain Iodine. Saturate the residual liquor of the manufacture of soap from kelp (or other iodine lye) of a specific gravity of 1.374, heated to 230° Fahr., with sulphuric acid diluted with half its weight of water; cool, decant the clear, strain, and to every 12 fluid ounces add 1000 grains of black oxide of manganese, in powder; put the mixture into a glass globe, or matrass with a wide neck, over which invert another glass globe, and apply heat with a charcoal fire; iodine will sublime very copiously, and condense in the upper vessel, which, as soon as warm, should be replaced by another; and the two globes thus applied in succession as long as violet vapor arises. It may be washed out of the globes with a little cold water. A thin disc of wood, having a hole in its centre, should be placed over the shoulder of the matrass, to prevent the heat from acting on the globular receiver. On the large scale, a leaden still may be employed, and receivers of stoneware economically substituted for glass ones. The top of the leaden still is usually furnished with a moveable stopper, by which the process may be watched, and additions of manganese or sulphuric acid made, if required. The addition of the sulphuric acid should be made in a wooden or stoneware basin or trough. To render the iodine pure, it should be dried as much as possible, and then resublimed in a glass or stoneware vessel. (Ure.)

Or: Extract all the soluble part of kelp by water, and crystallize the soda by evaporation ; to the mother-lye add oil of vitriol in excess, and boil the liquid, then strain it to separate some sulphur, and mix the filtered liquor with as much manganese as there was oil of vitriol: on applying heat, the iodine sublimes in the form of greyish-black scales, with a metallic lustre. The boiling is conducted in a leaden vessel; and a cylindrical leaden still with a very short head, and connected with 2 or 3 large globular glass reciv-ers, is used for the subliming apparatus. Care must be taken to watch the process, and prevent the neck of the still becoming choked with condensed iodine. ( Cooley.)