CHAPTER V. TANNING PROCESSES. More than one hundred tanning processes have been patented in the United States and Europe, and the cry is, “still they come.” New methods, and new works upon old methods are constantly presenting themselves. The London Mechanics’ Magazine states that an important improvement in the tanning of skins and hides has recently been introduced into that country by M. Funcke, a practical tanner and currier, of Herdecke, Westphalia. It consists in counteracting a too rapid action of the tannic acid upon the surface of the skins. The mode of operation is as follows:— The unhaired skins or hides are first passed through a weak liquor of the soda of commerce, then hung up to dry. They are then steeped in a common oak, hemlock, or other tanning liquor of the common strength, to which has been added some vinegar. In this liquor the pores of the skin are opened, and thus the tannic acid is admitted to the interior. The next tannic liquor in which the skins are steeped is made a little stronger with the bark, also some more vinegar, and a little dissolved sugar is added. The succeeding liquors to which the hides are subjected, until they are finished, do not differ from those in common use. The vinegar being a vegetable acid, unites with the alkali of the soda in the hides, and its carbonic acid is set free in the pores of the skin; this expands them, and allows the tannin admission to the centre of the hides in the first tanning liquor. The sugar in the second tannin liquor, unites with the vinegar, and forms a tannin mixture, it is said, which is of a softening character, imparting elasticity to the leather. The strength of the soda ley used to steep the hides in the first stage, is not above 1°—very weak—and a very small quantity of vinegar is sufficient for the purpose stated. Any other vegetable acid may be used in place of the vinegar, but it is the cheapest. The expanding of the pores of hides and skins by generating a gas in the tanning liquor by the agency of the carbonate of soda and an acid, such as sulphuric and muriatic, is not new. It has been tried in this country, and is known by the name of the “Hibbard process.” THE PRELLER PROCESS. This discovery and application is highly approved of in London.