The liquid known by this name, and formed on passing Sulphuretted Hydrogen gas into Ammonia, is a double Sulphuret of Hydrogen and Ammonium. In the preparation, the passage of the gas is to be continued until the solution gives no precipitate with Sulphate of Magnesia, and smells strongly of Hydrosulphuric Acid. _Properties._--Colourless at first, but afterwards changes to yellow, from liberation and subsequent solution of Sulphur. Becomes milky on the addition of any acid. Precipitates, in the form of Sulphuret, all the metals which are affected by Sulphuretted Hydrogen, and, in addition, those of the class to which Iron, Zinc, and Manganese belong. Hydrosulphate of Ammonia is employed in Photography to darken the Negative image, and also in the preparation of Iodide of Ammonium, the separation of Silver from Hyposulphite solutions, etc. HYPOSULPHITE OF SODA. Symbol, NaO S{2}O{2} + 5 HO. Atomic weight, 125. The chemistry of Hyposulphurous Acid and the Hyposulphite of Soda has been sufficiently described at pages 43, 129, and 137 of the present Work. The crystallized salt includes five atoms of water of crystallization. HYPOSULPHITE OF GOLD. _See_ Gold, Hyposulphite of. HYPOSULPHITE OF SILVER. _See_ Silver, Hyposulphite of. ICELAND MOSS. _Cetraria Islandica._--A species of Lichen found in Iceland and the mountainous parts of Europe; when boiled in water, it first swells up, and then yields a substance which gelatinizes on cooling. It contains Lichen Starch, a bitter principle soluble in Alcohol, termed "Cetrarine," and common Starch; traces of Gallic Acid and Bitartrate of Potash are also present. IODINE. Symbol, I. Atomic weight, 126. Iodine is chiefly prepared at Glasgow, from _kelp_, which is the fused ash obtained on burning seaweeds. The waters of the ocean contain minute quantities of the Iodides of Sodium and Magnesium, which are separated and stored up by the growing tissues of the marine plant. In the preparation, the mother-liquor of kelp is evaporated to dryness and distilled with Sulphuric Acid; the Hydriodic Acid first liberated is decomposed by the high temperature, and fumes of Iodine condense in the form of opaque crystals. _Properties._--Iodine has a bluish-black colour and metallic lustre; it stains the skin yellow, and has a pungent smell, like diluted Chlorine. It is extremely volatile when moist, boils at 350°, and produces dense violet-coloured fumes, which condense in brilliant plates. Specific gravity 4·946. Iodine is very sparingly soluble in water, 1 part requiring 7000 parts for perfect solution; even this minute quantity however tinges the liquid of a brown colour. Alcohol and Ether dissolve it more abundantly, forming dark-brown solutions. Iodine also dissolves freely in solutions of the alkaline Iodides, such as the Iodide of Potassium, of Sodium, and of Ammonium.