A bating liquor which was proposed by the writer, and which has been used with some success on harness-leather, is made up with a ¹⁄₄ lb. of good white ammonium chloride (sal ammoniac) and a ¹⁄₄ lb. of Boakes’ “metabisulphite of soda” per hide, and for successive packs sufficient sulphuric acid to neutralise the ammonia formed, together with a small quantity of metabisulphite and ammonium chloride to restore that carried out by the hides is added. It is probable that this would also answer well for deliming sole-leather as it entirely removes lime without pulling down the hides much, and they would remain still plumper if ammonium sulphate were substituted for ammonium chloride, while the sulphuric acid might be safely increased till the liquor was but slightly alkaline when the bating was finished. About 2-4 oz. of good white oil of vitriol is required per hide, but the exact quantity will depend on the mode of liming, and the amount of washing the hides receive before going into the bate, and can therefore be only ascertained by experience. As no free sulphuric acid can exist in the liquor so long as the quantity of metabisulphite is maintained, there is no practical danger of spoiling the leather if the acid be in slight excess. The quantities given may in most cases be advantageously diminished, since it is not always advisable in practice to remove the whole of the lime, which in small quantity renders tannage and penetration of the liquor much more rapid, either by acting as a mordant to the tannin, or by temporarily neutralising it and diminishing its astringent action on the hide-fibre. Turning to dressing leather, we find that the use of cold water alone has been practically abandoned in this country, though the finest French calf is produced by repeated soakings in cold water with alternate workings over the beam, sometimes extending to nine or more. In this case, from the lengthened exposure to waters which are only gradually renewed it is probable that putrefactive action takes place, and that a sort of bating is effected by the decomposing products of the hide itself; in fact, in many French yards, bran-drenches have been introduced to supplement the action of the water alone. Waters differ greatly in their power of removing lime from skin. Slightly acid and peaty waters, and those in general which contain much organic matter, are much more powerful in reducing than those which are purer (cp. p. 107). Warm water has much more effect in removing lime than cold, since the heat lessens the risk of dissolved carbonic acid, and seems to have a direct depleting effect on the pelt. A good tumbling in warm soft water will remove a great deal of lime, and is an excellent preparation for bating, but heat must be used cautiously, and should never exceed 30°-35° C.; some skins, such as seals, being very readily tendered by its action, while others, especially sheep-skins, will stand a comparatively high temperature.