On Gold Refining by Chlorine Gas. 161 



square gold-melting furnace, the principal points to attend to in 

 its construction being — 1st, that the flue should be as near the 

 top as possible, so as to allow of the crucible standing high up in 

 it without being cooled by the draught ; and, secondly, that the 

 furnace itself should not be too deep, so that when the pot is 

 placed in the fire the bottom of it may not be more than three 

 inches above the bars. 



The covering of the furnace should consist of two fire tiles, 7i 

 inches wide and 15 inches long, one of which should have a long 

 slot or hole in its centre for the clay chlorine pipes, which I shall 

 describe presently, to pass through. An iron cover will not 

 answer, as it soon becomes much too hot for convenient working. 



The crucibles in which the refinage is performed should be 

 French white fluxing pots (creusets de Paris, made by De Euelle, 

 late Payen, Paris), ordinary black lead pots will not answer, 

 owing to the reducing action they exert on the compounds 

 formed. To prevent the infiltration of the very fluid chloride of 

 silver into the pores of the clay pots, which would otherwise 

 occur, and necessarily entail loss, they are prepared, by filling 

 them with a boiling saturated solution of borax in water, which 

 is allowed to stand in them for ten minutes, and is then poured 

 off; the crucibles being afterwards set aside to dry, the borax 

 forms a glaze on the inner surface of the crucibles when they 

 become hot in the furnace. 



"When used for refining, these French clay crucibles are placed 

 within black-lead pots, as a precaution against loss, should 

 the former crack, which, however, seldom happens. The crucibles 

 are covered with loosely fitting lids, with the requisite holes 

 bored through them for the passage of the clay chlorine pipes, 

 &c. Ordinary clay tobacco pipe stems, from 17 to 22 inches 

 long, have been found to answer well for the purpose of passing 

 the chlorine gas through the melted gold. Of late, a pipe made 

 in London to order, f an inch in diameter. 22 inches long, and 

 3-16 inch bore, has been found to answer all requirements. 

 The chlorine generators should consist of the best glazed stone- 

 ware acid jars, capable of holding from ten to fifteen gallons, and 

 furnished with two necks. One of these openings should be 

 stopped with a sound cork, or vulcanised indiarubber plug, if 

 obtainable, through which should pass tightly two glass tubes, 

 the eduction tube, and the safety or pressure tube, the length of 

 the former being a few inches, and the latter eight or ten feet, 

 spliced where necessary by means of vulcanized indiarubber 

 tubing. The other opening, intended for introducing the oxide 

 of manganese, &c, should be closed with a leaden plug covered 

 with a short piece of indiarubber tube by way of a washer, and 

 well secured. 



Each generator should be charged with a draining layer of 



