_Lotio Nigra (Lot. Nigr.), Black Lotion, N.F._ (Black Wash, Aqua Phagedaenica Nigra).--A suspension of mercurous oxide, Hg{2}O, produced by the action of lime water on mild mercurous chloride. USES: Mercurial antiseptic. _Pulvis Hydrargyri Chloridi Mitis et Jalapae (Pulv. Hydrarg. Chlor. Mit. et Jalap.), Powder of Mild Mercurous Chloride and Jalap, N.F._ (Calomel and Jalap).--Mild mercurous chloride (34%) and jalap (66%). USES: Drastic purgative. DOSAGE: 0.65 Gm. or 10 grains (N.F.) =*Hydrargyri Iodidum Flavum (Hydrarg. Iod. Flav.), Yellow Mercurous Iodide, U.S.P.= (Mercurous Iodide, Protoiodide of Mercury, Yellow Iodide of Mercury).--HgI. Bright yellow, odorless, tasteless powder. Almost insoluble in water and wholly insoluble in alcohol or ether. Decomposed by oxidizing agents, alkalies and the haloid salts of the alkali metals (chlorides, bromides or iodides). ACTION AND USES: Used principally as an antisyphilitic; generally given in the form of pills. Like all ingestion methods of treating syphilis, much less reliable than the intramuscular administration of mercurials and is falling into disuse on account of relative inefficiency. Has proved of value in lichen ruber planus. DOSAGE: 0.01 Gm. or 1/6 grain (U.S.P.) =*Hydrargyri Iodidum Rubrum (Hydrarg. Iod. Rub.), Red Mercuric Iodide, U.S.P.= (Biniodide of Mercury, Mercuric Iodide, Red Iodide of Mercury).--HgI{2}. Scarlet-red, odorless, nearly tasteless powder. Nearly insoluble in water and slightly soluble in alcohol (1:115); soluble in solutions of soluble iodides, sodium thiosulphate and hot solutions of alkali chlorides. ACTION AND USES: Mercuric Iodide, dissolved with potassium or sodium iodide, is used as an antiseptic, germicide and antisyphilitic. It is practically as effective as mercuric chloride and less irritant or corrosive. DOSAGE: 0.003 Gm. or 1/20 grain (U.S.P.). _Liquor Hydrargyri et Potassii Iodidi (Liq. Hydrarg. et Pot. Iod.), Solution of Mercury and Potassium Iodide, N.F._ (Solution of Potassium Iodohydrargyrate, Channing's Solution).--Red mercuric iodide (1%), potassium iodide (0.8%), and water. DOSAGE: 0.2 Cc. or 3 minims (N.F.) =Hydrargyri Nitras, Mercuric Nitrate.=--Hg(NO{3}){2}. _Liquor Hydrargyri Nitratis (Liq. Hydrarg. Nit.), Solution of Mercuric Nitrate, N.F._--Hg(NO{3}){2} (60%). USES: Caustic. _Unguentum Hydrargyri Nitratis (Ung. Hydrarg. Nit.), Ointment of Mercuric Nitrate, U.S.P._ (Citrine Ointment).--Mercuric nitrate (equivalent to mercury 7%) in lard. =*Hydrargyri Oxidum Flavum (Hydrarg. Oxid. Flav.), Yellow Mercuric Oxide, U.S.P.=--HgO. Light orange-yellow, heavy, odorless powder, with a somewhat metallic taste. Almost insoluble in water, insoluble in alcohol, readily dissolved by dilute hydrochloric acid and nitric acid.