_Commercial Creasote._—When obtained from coal tar is always contaminated with phenylic acid (carbolic acid.) Indeed, it is said that phenylic acid has been sold for creasote, which it closely resembles in properties. How far these properties may be similar, deserves to be studied; for if they should prove to be the same, the fact would lead to its substitution as a substance to be easily obtained pure, for the variable creasote. Of all the properties of creasote, the most remarkable is its power of preserving animal matter; this property has suggested its name, derived from two Greek words which mean flesh preserver. Dr. Christison finds that creasote water is as good a preservative of anatomical preparations as alcohol, with the advantage of not hardening the parts; it is probably to creasote that the antiseptic properties of pyroligneous acid are owing. _Tannic Acid._—Some powder of nut galls is macerated in a bottle, with just enough ether to moisten it, for 24 hours, and then expressed in a powerful press; and the process of maceration and expulsion is repeated in the same way until the powder is exhausted; the liquors are mixed, the ether distilled off, and the residue dried by means of a water bath. Properties: Pure tannic acid is solid, uncrystallizable, white or slightly yellowish, inodorous; very soluble in water, and much less soluble in alcohol and ether, and insoluble in the fixed and volatile oils. Tannic acid precipitates solutions of starch, albumen and gluten, and forms with gluten an insoluble compound which is the basis of leather. _Chromic Acid._—To 100 parts, by measure, of cold saturated solution of bichromate of potassa, 150 parts of sulphuric acid are added and allowed to cool; the sulphuric acid unites with the potassa, and the chromic acid crystallized in deep red needles, very soluble and deliquescent. It is a powerful oxydizing and bleaching agent. Small animals, as mice, etc., after being immersed in the acid were so completely dissolved after 20 minutes, that no traces were left of either their claws, hair, bones or teeth. _Sulphurous Acid._—It is prepared by exposing to heat a mixture of one part concentrated sulphuric acid with one part of mercury, or one-third part of copper filings, washing the gas by passing it through a little water, and condensing it in water which is well cooled. Professor Proctor directs the gas evolved from four ounces of copper turnings, and eight fluid ounces of sulphuric acid, to be condensed into four pints of water. Sulphurous acid is a gas which dissolves largely in water and has a smell of burning sulphur. _Liquor Chlorinated Soda—Labarraque Disinfecting Solution._—It is prepared as follows: Chloride of Lime, 1 pound, Carbonate of Soda, 2 pounds, Water, 1½ gallons.