292 



CHAPTER XVI 



on a tray. The combustion of the sulphur may take place with free access 

 to the atmosphere, a draught being obtained by a fan or jet of exhaust steam, 

 as in connection with the " sulphur box " described below. Direct access 

 to the atmosphere is, however, to be avoided, since in the presence of water 

 sulphur burns in part to the trioxide, giving rise to sulphuric acid in the juices, 

 the presence of which is objectionable. The air admitted for combustion 

 should therefore be dried by passing through quicklime before it reaches the 

 oven. A very simple and convenient dryer may be made from a piece of iron 

 pipe about six inches in diameter and four feet high, and holding about 

 forty lbs. of coarse lime. As required, depending on the humidity of the 

 air and the quantity of sulphur burned, the lime is renewed. The fire area 

 of the stove depends on the draught or on the air pressure when compressed 

 air is employed. With a draught of two to three inches of water two lbs. 

 of sulphur can be burnt per sq. ft. per hour. As the sulphur burns the rise 

 in temperature causes some part to sublime, and this being carried forward 





^^ 



a 



-^^vvs^^^s^^^■^<^^^^^^^^ ^ 



?zz: 



>SSSSSSS.S.S.^SS\NSV z. 



rj^^j'^^^^^^^^:^. 



Fig. 172 



will|in time cause the pipes to become'^choked. The'oven^should therefore 

 be provided with a water-cooled dome serving to condense the sublimate, 

 and from which it may be periodically removed. The sulphur furnaces are 

 of such simple construction that they^may^be readily made on the plantation. 

 For continuity of operation they are conveniently used in pairs. 



The means for the absorption of the gas may be the sulphur " box " or 

 tower indicated in Fig. 170. This consists of a wooden vertical shaft, in 

 which are arranged perforated trays e. The juice is delivered to the top of 

 the box by the pipe h, and flowing down meets a stream of gas entering by the 

 pipe c, and travelling upwards under the influence of the draught caused by 

 the steam jet a. In place of perforated trays other arrangements borrowed 

 from the condenser may be used. In place of the tower it is better practice 

 to sulphur the juice or syrup in tanks, and in this case the gas must be pumped 

 to the tank or conveyed thereto by means of an ejector or by compressed air. 

 A diagrammatic scheme of such an arrangement is shown in Fig. 171, where 

 a represents the ovens with water-cooled domes, h the air compressor, c towers 

 packed with coke or similar material serving as a filter, d a chamber filled 

 with dry lime, e the sulphitation tanks and /the conducting piping. Another 



