It is to be borne in mind that in all cases of using acids, any carbonate of lime present on the pit sides or elsewhere will be decomposed, and the carbonic acid will become dissolved in the liquor, and unless acid is used in sufficient quantity to remove the whole of the lime, may tend to fix the remainder as carbonate. In the case of dressing leather there is less danger of this, as warm water is generally used, in which little carbonic acid dissolves. It is probable that some of the coal-tar acids which have been advertised for bating dressing leather might be advantageously employed for sole. Hauff’s “anticalcium” (see pp. 29, 163), would appear to be very suitable for this purpose, and if the liquor were regenerated by the addition of sufficient sulphuric acid to neutralise the lime dissolved from the hide, might be used repeatedly, and would not then prove expensive; while its sterilising power would be very advantageous to the proper swelling of the butts in the handlers, since nothing tends to check plumping so much as putrefactive action. Turning from sole to dressing leather, mineral acids are very successfully employed for “pulling down,” the goods being thrown into a paddle containing warm water of about 30°-35° C., and the calculated quantity of sulphuric or hydrochloric acid, previously largely diluted with water, is then added in two or three successive portions at intervals of perhaps ten minutes. The acid must in no case be sufficient to neutralise quite the whole of the lime. Goods treated in this way can be further bated, puered, or drenched as required by the ordinary methods, if they are not sufficiently soft. If too much acid has been used, and the skins show signs of swelling, they may be brought down by the addition of a little ammonia, borax, or even soda.