_Blue Mass_ or _Blue Pill_ (Massa Hydrargyri).—This is a mixture of mercury, glycerin, honey, and licorice. Its action is much like that of calomel. _Corrosive Sublimate_ or _Bichlorid of Mercury_ (Hydrargyri Chloridum Corrosivum).—Although irritant, toxic, and destructive to instruments, no other drug has supplanted this salt as an antiseptic for use in general surgery. The following are the strengths of the solutions usually employed for various purposes: for the skin, 1 : 1000 to 1 : 500; for wounds, 1 : 10,000 to 1 : 2000; for cavities of the body, 1 : 20,000 to 1 : 5000. Corrosive sublimate is not a good disinfectant for stools, sputa, etc., as it forms an impenetrable coagulum on the outside of the mass. Internally, corrosive sublimate is used as an alterative in constitutional diseases in _doses_ of ¹/₆₀ to ¹/₁₂ of a grain (0.001-0.005 gm.). _Oxid of Mercury._—This appears in two forms—yellow oxid and red oxid. Both preparations are employed externally in the form of ointments for their alterative properties. _Iodid of Mercury._—This salt occurs in two forms: Red Iodid or Biniodid (Hydrargyri Iodidum Rubrum) and Yellow or Green Iodid (Hydrargyri Iodidum Flavum). The first is an irritating preparation, somewhat resembling corrosive sublimate in its action; the latter is comparatively unirritating, and is much used internally as an alterative. The _dose_ of the _red iodid_ is from ¹/₆₀ to ¹/₁₂ grain (0.001-0.005 gm.); of the _yellow_ or _green iodid_, ¹/₁₀ to ½ grain (0.006-0.03 gm.). _Nitrate of Mercury._—This preparation is used in the form of a solution (Liquor Hydrargyri Nitratis) as a powerful caustic. _Ointment of Mercury_, or _Blue Ointment_ (Unguentum Hydrargyri).—This is an ointment of metallic mercury. It is used as a stimulant and absorbent application in chronic inflammatory swellings, as a parasiticide in certain skin diseases, and by inunction in syphilis. When used for the latter purpose about a dram (4 gm.) should be rubbed in the axilla, groin, or inner surface of the arm or thigh daily, a different region being selected each time, so as to avoid irritation of the skin.