5. In baths of the Schultz and neutral type it is better to add some acid to the hypo bath before adding the goods, but this is less essential for goods from an acid chroming bath. 6. In the case of goods from acid chroming baths, the amount of acid used in the reducing bath is an inverse function of the excess of acid in the first bath, _e.g._ take the following two processes:-- ------------------------------------+------------------------------- Chroming bath. | Hypo bath. ---------------+--------------------+----------+-------------------- Dichromate. | Hydrochloric acid. | Hypo. | Hydrochloric acid. ---------------+--------------------+----------+-------------------- 4 | 4 | 12 | 5 4 | 15 | 15 | 1 ---------------+--------------------+----------+-------------------- 7. There should be some excess of hypo at the end of the process. This acts as a feeble alkali, and commences the neutralization. The process can be carried out in paddles or in drums as preferred, for reasons similar to those applicable in the case of the first bath. On the whole, however, drums are less popular for the second bath, for the dilute solutions of the paddle effect some economy of sulphurous acid, which is apt to escape into the air. A preliminary "hypo dip" is sometimes used to prevent the "bleeding" of the chromic acid. The use of many other reducing agents has been suggested as substitutes for hypo. Sulphides, sulphuretted hydrogen, polysulphides, sulphites, bisulphites, hydrogen peroxide, nitrous acid, lactic acid, etc., have been used, but none are so easy to manipulate as thiosulphate.