CLEARING THE BATH.
A variety of methods. are adopted for this purpose ; the best is to expose the bath to strong daylight—sunlight if pos sible—for about a. clay, when the organic matter will reduce a small portion of the silver, which falls to the bottom of the vessel. The clear solution may then be decanted off, or syphoned by means of a jar fitted with bent tubes, as shown in Fig. 262. This apparatus con sists of a wick-mouthed jar fitted with a bung, which is bored to accommodate the bent tubes A and B. The bent tube should reach almost to the bottom of the jar, it exact position being dependent upon the amount of precipitate present. as it shout be just above this. It is easily raised tc the proper height. By blowing down tub( A the solution will be forced out at R, ant will continue to run until the bottle empty. The objection to this method that the bath must be put out of use fol a whole day ; but where two baths are kept. going, in case of accidents, this wil
not prove a serious inconvenience. A quid way to bring down the organic matter i to add a very small quantity of hydro. chloric acid. This will result in the for oration of silver chloride and nitric acid thus :— AgNO, + HC1 = Age.' + (Silver nitrate and hydrochloric acid forn silver chloride and nitric acid.) After thi: addition the solution must be tested witl litmus paper, even if silver carbonate ha been present in the solution. If showim an acid reaction, sufficient soda carbonat must be added to neutralise it. A bette method, and one in practical use in mos establishments in winter, is to add a littl Kaolin or China clay, which carries (low] the finely divided precipitate. See tha le Kaolin is pure ; if adulterated it i seless and injurious.