SULPHITATION 



293 



tvpe of oven which operates satisfactorily is shown in Fig. 172. It consists 

 of an iron oven \\ith a heav\'door, h, resting on and making a tight joint -with 

 a rubber seat and covering the aperture through which the sulphur is period- 

 ically introduced. The draught is obtained by means of the injector e using 

 Uve steam, and affording sufficient head to force the gas into the tanks. 

 The air enters through the pipe c, which is packed with dry lime. The in- 

 jector may be made of lead alloyed with three per cent, of antimony. 



.\n apparatus ver\' widely used in the beet sugar industry is that of 

 Quarez, Fig. 173. The juice nms from the mills through the pipe B into 

 the tank A, divided into two compartments by the plate C reaching nearly 

 to the bottom. From here it is forced by the pump D through the injector E, 

 which conunimicates by the piping H 

 with the sulphur furnace G, so that the 

 gas is drawn into the juice, which now 

 travels by the pipe K into the tank, 

 whence it overflows through the pipe 

 i\/. In this arrangement the quantity 

 of juice passing regulates the rate at 

 which the sulphur is burned. 



A method of sulphuring which was 

 once largely used in the beet sugar in- 

 dustr\' is that of Se\-ferth (patent 

 2756 of 1870), which drew the gas 

 direct!}- into the vacuum pan during 

 the operation of boHing. This scheme 

 is only exceptionally to be found in 

 the cane industry. 



Quantity of Sulphur used. — In the 



different schemes this wiU depend on 

 the quantity of lime used and on the 

 acidity desired. Starting with a neu- 

 tral juice, each ic.c. of normal acidity 

 per 100 c.c. of juice corresponds to the 

 presence of o-i6 gram sulphur per 

 1,000 c.c, or ver\' closely to o-oi6 Fig. 173 



sulphur per cent, on cane, when the 



weight of juice is the same as that of the cane. x\ctually when using 

 sulphur only on second carbonated juices the consumption is found to 

 be about o-02 per cent, on cane, in sulpho-defecation processes about 

 0-04 per cent, on cane, and in Bach's scheme it rises to o-i per cent. 

 on cane. As sulphur burning to 502 requires oxygen equal to the weight 

 of the sulphur, the air required will be 4-5 lbs. Actually due to ineflicienc\' 

 9 lbs. air should be allowed in design. The volume of air remaining imchanged 

 diuing combustion, per lb. of sulphur there will be at the normai temperature 

 125 c. ft. to be pmnped. The maximum volume per cent, of sulphiu: dioxide 

 in the gas will be 20-8 per cent., and with twice the necessary- quantity of 

 air admitted this wiU fall to 10-4 per cent. These data give all the essentials 

 required for design. 



Hydrosulphites. — The bleaching effect of hydrosulphurous acid was first 

 employed in Ranson's process,^ which passes sulphur dioxide into juices 



