Peroxide of hydrogen, or hydrogen dioxide, is at the present time made on a large scale by many manufacturers, and readily obtainable in the market. It would therefore scarcely pay any one to prepare it himself unless he were out of reach of the usual channels of trade, so that he could not obtain the preparation in a _fresh_ state. Nevertheless it may be useful to state how it is made. Barium dioxide (or peroxide), which is a regular article of commerce, and is a stable compound which will keep for any length of time if kept in tightly closed bottles, is treated with water until the dioxide forms with it a thin, smooth milk. This is gradually added to dilute sulphuric acid, cooled with ice or kept otherwise as cold as possible, until the sulphuric acid is almost entirely neutralized. The solution is then allowed to settle and the clear liquid drawn off. For bleaching purposes, this is pure enough. Only it must be ascertained that the amount of free acid present, without which the hydrogen dioxide does not keep well, is only small. Other acids can be used besides sulphuric, but the latter is the most convenient. If an alkali is added to hydrogen dioxide so that the reaction becomes alkaline, it will decompose very rapidly. Even under the most favorable circumstances (when acid, and kept in a cool place) it will gradually deteriorate, and finally be entirely converted into oxygen gas, which escapes, and plain water. Peroxide or dioxide of hydrogen, when applied to the hair as a bleaching agent, must be used in a dilute condition at first. Those who use it for the first time should always make preliminary trials with the liquid upon odd bunches of hair (such as may at any time be procured at hair-dressers’ shops) resembling that which is to be bleached, before actually applying it to the latter. The hair to be bleached is deprived of fat by washing with soap solution, the soap is washed out with water, and the peroxide of hydrogen applied. WHISKER DYE. I. Acetate of lead 1¾ oz. Distilled water 1 pint. II. Caustic potassa ¾ oz. Distilled water 1 qt. Dissolve the acetate of lead (“sugar of lead”) in the warm water, filter the solution, and add ammonia water until a precipitate ceases to form. Collect the precipitate on a filter, wash it by pouring distilled water over it eight or ten times, and while still moist introduce it into solution II. Stir repeatedly, and after twelve hours leave the vessel at rest until the solution has become clear. Then decant it from the sediment, which may be treated a second time with solution II. For use, the beard is washed with soap, and combed with a fine rubber comb dipped in the solution. C. Depilatories.