The solution of peroxide of hydrogen is obtained by decomposing peroxide of barium by hydrochloric or hydrofluoric acid in the presence of ice-cold water. The solution usually contains from three to five per cent, of the peroxide. It is a colorless, transparent liquid, without odor, and a harsh and bitter taste, soluble in water in all proportions. It decomposes slowly in the cold, but quickly at a higher temperature, and when exposed to the sunlight; it must therefore be kept well stoppered in a cool and dark place. It is comparatively a new, but powerful antiseptic, possesses active powers to arrest and prevent fermentation, and is safe in regard to health. Used by car-bonators in preserving beverages, and solutions of citric acid, etc., it does valuable service. How far its preventative properties go, is not exactly known, but it is said that beer, wine, cider, and similar fermented drinks containing a few drops of it, did not exhibit the least sign of fer-mentation, even after an exposure of several months in open vessels. We employed about three drachms to a gallon of syrup with excellent results. A half-pint bottle (one ounce of syrup to the bottle) will then contain about 1.5 grains, an entirely harmless, but effective quantity.