Messrs. Pullman now recommend that the treatment with their solutions should take place in pits, in preference to drums or paddles, and that the caustic soda should not exceed a strength of one pound in ten gallons (1 per cent.). The hides or calf-skins remain in this for about forty-eight hours, during which they are once drawn and returned, by which time, if the putrid soaking has been properly done, the hair should be fully loosened. The hides are then drained for two hours, and passed into another pit containing a solution of calcium chloride, which should be slightly stronger than the caustic soda, say of about one and a half pounds per ten gallons. The goods remain in this for about forty-eight hours, during which they are drawn once, and are then well washed in soft water (free from temporary hardness) in which they may be kept for some time without injury. As both the caustic soda and the calcium chloride solutions are quite sterile to ordinary putrefactive bacteria, both can be used for an almost unlimited time, and they are conveniently kept up to strength by the addition of strong stock-solutions. These may be made of a sp. gr. of 1·4 (80 deg. Tw.) which gives a strength of about 5¹⁄₂ lb. of caustic soda and 5³⁄₄ lb. of calcium chloride per gallon. In addition to the advantage of considerable saving of time, the effects can be much more easily regulated than in ordinary liming, and the amount of soda (and subsequently of lime) absorbed by the hide can be exactly determined by titration of the liquors. Grease is better removed than by ordinary liming, as soda-soaps are soluble in water, but if this result is to be obtained, the soap must be worked out before passing into the calcium chloride solution, which would otherwise convert it into an insoluble lime-soap. A great gain in many districts is that the process yields practically no effluents and no lime slab, both of which are frequently very difficult to dispose of. The serious disadvantages of the stale soaking, however, have already been mentioned. In place of applying the caustic soda first, and the calcium chloride subsequently, hides may be first treated with calcium chloride solution, and then with caustic soda, or the caustic soda may be applied to the flesh side of the hide by painting. These modifications are covered by Messrs. Pullman’s patent, but they are willing to grant licences for experiments at a nominal fee. _Alkaline carbonates_ are much milder in their action on hide than the corresponding hydrates, and although they will unhair hides, in absence of lime, their action is somewhat uncertain and slow. “Polysulphin” (Polysulphin Co., Keynsham) owes its unhairing power principally to the sodium carbonate, and not to the small traces of sulphur compounds which it contains.