_Manganese._--Manganese is the only metal which is precipitated only as peroxide. It is deposited at once on closing the circuit, and is at first brown, then black and shining. Organic acids, ferrous oxide, chromic oxide, ammonium salts, etc., prevent the formation of peroxide and the red color produced by permanganic acid. In very dilute strongly acid nitric solutions there is formed only permanganic acid, which according to Riche is plainly visible in solutions containing 1/1000000 grm. manganese. On electrolyzing a manganiferous solution of copper nitrate, red permanganic acid appeared in a stratum floating above the platinum disk coated with brown peroxide. No manganese peroxide was deposited. The peroxide adheres firmly to the platinum when the proportion of free acid is small, not exceeding 3 per cent., and the current is not too strong. If the action of the current is prolonged after the peroxide is thrown down, it falls off in laminae. According to Riche, in a nitric solution the manganese is deposited as peroxide, also at the negative pole. This formation is not directly due to the current, but is a precipitate occasioned by the production of ammonia by the reduction of nitric acid. To determine the manganese in peroxide electrolytically precipitated, it is heated to bright redness in the platinum capsule until the weight becomes constant. The results are too high. _Selenium and Tellurium._--Both these bodies are readily and completely reduced by the current either in acid or alkaline solutions. Selenium is thrown down at first of a fine brownish red, which gradually becomes darker. The deposit of tellurium is of a bluish black color. If the current is feeble, the deposit of selenium is moderately compact; that of tellurium is always loose, and it often floats on the liquid. A strong current precipitates both as powders. The positive pole is coated during electrolysis with a film of a dark color in case of selenium, but of a lemon yellow with tellurium. As in case of arsenic and antimony, the hydrogen evolved at the negative pole combines with the reduced substances, forming hydrogen, selenide, or telluride, which remain in part in solution in the liquid. The reduced metal separates out at the anode in a friable condition.--_Zeitschrift fur Analytische Chemie, and Chemical News._ * * * * * THE ELECTRO-CHEMICAL EQUIVALENT OF SILVER.