The operation of chlorination can be done either in one or two (p. 038) baths. The choice depends upon circumstances and the judgment of the dyer. The process by the two-bath method, with subsequent dyeing in the second or separate bath is (for 100 lb. of wool), as follows. The first bath contains, for light cloths, yarn, etc., from 3 to 4 lb. sulphuric acid, 168 deg. Tw., and for heavier cloths and felt, where the penetration and equalisation of the colour is difficult, from 8 lb. to 10 lb. of acid. Generally speaking, a temperature of 170 deg. to 175 deg. F. is sufficient, although for heavy wool and for wool with poor dyeing qualities it is well to use the bath at the boil. The treatment lasts for half an hour, in which time the acid is almost completely absorbed. The second bath contains a clear solution of 10 lb. bleaching powder, which solution is prepared as follows. Dry bleaching powder of the best quality is stirred in a wooden vat with 70 gallons of water, the mass is allowed to stand, the clear, supernatant liquor is run into the vat and the sediment stirred up and again allowed to settle, the clear liquor being run off as before, and 5 gallons more water is run in. The clear liquors of these three treatments are then mixed together to form the chloring bath. Special care should be taken that no undissolved particles of the bleaching powder should be left in, for if these settle on the wool they result in too great a development of chlorine, which injures the wool. The goods after being in the acid bath are entered in this chlorine bath at a temperature of 70 deg. F., which is then raised to the boil. If the acid bath has been strong, or been used at the boil, it is perhaps best to rinse the goods before entering into the chlorine bath. The hypochlorous acid disappears so completely from this bath that it may at once be used as the dye-bath, for which purpose it is only necessary to lift the goods, add the required amount of dye-stuff, re-enter the goods and work until the bath is exhausted, which generally happens when acid dyes are used. If a separate dye-bath be preferred, this is (p. 039) made and used as is ordinarily done. To perform all the operations in one bath the acid bath is made with from 3 to 4 lb. sulphuric acid, and the wool is treated therein for thirty minutes at 170 deg. F., until all the acid has been absorbed. Then the bath is allowed to cool down to 70 deg. or 80 deg. F., the clear bleaching powder solution is added, the goods are re-entered, and the bath is heated to the boil. When all the chlorine has disappeared add the dye-stuff, and dye as directed above.