SULPHUR 



955 



Pouzzales, near Naples, where the sulphur is condensed in considerable quantities 

 amongst the gravel collected in the circle "which forms the interior of the crater, is 

 conducted as follows : the mixture of sulphur and gravel is dug up and submitted to 

 distillation to extract the sulphur, and the gravel is returned to its original place, and 

 in the course of about thirty years is again so rich in sulphur as to serve for the same 

 process again. The distillation is effected in the following manner : Ten earthen 

 pots, of about a yard in height, and 4 gallons imperial in capacity, bulging in the 

 middle, are ranged in a furnace called a gallery ; five being set on the one side, and 

 five on the other. These are so distributed in the body of the walls of the gallery, 

 that their belly projects partly without and partly within, while their top rises out of 

 the vault of the roof. The pots are filled with lumps of the sulphur ore of the size 

 of the fist; their tops are closed with earthenware lids, and from their shoulder 

 proceeds a pipe of about 2 inches diameter, which bends down, and enters into another 

 covered pot, with a hole in its bottom, standing over a tub filled with water. On ap- 

 plying heat to the gallery, the sulphur melts, volatilises, and runs down in a liquid 

 state into the tubs, where it congeals. When one operation is finished, the pots are 

 re-charged, and the process is repeated. 



The sulphur thus obtained is still more or less impure, and in this case can only bo 

 used in the manufacture of sulphuric acid ; it is therefore subjected to another process 

 of purification, which will now be described : 



Fig. 1942 represents one of the cast-iron retorts used at Marseilles for refining 

 sulphur, wherein it is melted and converted into vapours, which are led into a large 

 chamber for condensation. The body, a, of the retort is an iron pot, 3 feet in 

 diameter outside, 22 inches deep, half an inch thick, which weighs 14 cwts., and 

 receives a charge of 8 cwts. of crude sulphur. The grate is 8 inches under its bottom, 

 whence the flame rises and 



plays round its sides. A cast- 

 iron capital, b, being luted to 

 the top, and covered with sand, 

 the opening in front is shut 

 with an iron plate. The chamber 



d, is 23 feet long, 11 feet wide, 

 and 13 feet high, with walls 32 

 inches thick. In the roof, at 

 each gable, valves or flap-doors, 



e, 10 inches square, are placed 

 at the bottom of the chimney a. 

 The cords for opening the valves 

 are led down to the side of the 

 furnace. The entrance to the 

 chamber is shut with an iron 

 door. In the wall opposite to 

 the retorts, there are two aper- 

 tures near the floor, for taking 

 out the sulphur. Each of the 

 two retorts belonging to 

 chamber is charged with 7i < 



1942 



8 cwts. of sulphur ; but one is fired first, and with a gentle heat, lest the brimstone 

 froth should overflow ; but when the fumes begin to rise copiously, with a stronger 

 flame. The distillation commences within an hour of kindling the fire, and is com- 

 pleted in six hours. Three hours after putting fire to the first retort, the second is 

 in like manner set in operation. 



When the procews of distillation is resumed, after having been some time suspended, 

 explosions may be apprehended, from the presence of atmospheric air : to obviate 

 the danger of which, the flap-doors must be opened every 10 minutes ; but they should 

 remain closed during the setting of the retorts, and the reflux of siilphurous fumes or 

 acid should be carried off by a draught-hood over the retorts. The distillation is 

 carried on without interruption during the week, the charges being repeated four 

 times in the day. By the third day, the chamber acquires such a degree of heat as to 

 preserve the sulphur in a liquid state ; on the sixth, its temperature becoming nearly 

 300 Fahr., gives the sulphur a dark hue, on which account the furnace is allowed to 

 cool on the Sunday. The fittest distilling temperature is about 248. The sulphur is 

 drawn off through two iron pipes cast in the iron doors of the orifices on the side of 

 the chamber opposite to the furnace. The iron stoppers being taken out of the mouths 

 of the pipes, the sulphur is allowed to run along an iron spout placed over red-hot 

 charcoal, into the appropriate wooden moulds. 



Other forms of apparatus have been used of lato years in Italy for the extraction of 



