NORTHERN SUGAR INDUSTRY. 



97 



MANUFACTURE OF SULPHUROUS DIOXIDE (SOg). 



(I.) The simplest method of mau ufac taring this article is by burning 

 sulphur. This should be done in furnaces made of fire-brick, since hot 

 iron is readily attacked by sulphur. 



(2.) Sulphurous dioxide is also readily tormed by heating charcoal 

 with strong sulphurous acid (oil of vitriol). 



(3.) It may also be made by treating some sulphite or bisulphite (as 

 lime, &c.) with a stronger acid, e. g.^ oil of vitriol. 



The sulphurous acid used in sugar or sirup making is manufactured 

 in one of the three ways mentioned. 



PROPERTIES. 



Sulphurous dioxide (or acid) is a colorless gas, more than twice as heavy 

 as air. Its odor is familiar in the fumes of a burning sulphur match. The 

 gas is very soluble in water, 1 volume of the latter absorbing about 

 40 volumes of the gas at ordinary temperature. One litre of water, 

 therefore, will absorb nearly 115 grams of the gas, or one gallon of water 

 at 60^ F. saturated with the gas will contain of it a little more than 10 

 ounces. 



In aqueous solution sulphurous acid (it becomes an acid by solution 

 in water) easily undergoes oxidation, and its bleaching power is due to 

 this process, by which nascent hydrogen is set free, which attacks the 

 coloring matter. An equivalent amount of sulphuric acid is always 

 formed. It is therefore advisable to use lime (or some base which will 

 form an insoluble compound) with sulphurous acid in order to form a 

 precipitate with the sulphuric acid which is produced. 



Sulphurous dioxide, by a freezing mixture (as ice and salt), or by 

 pressure, is easily condensed to a colorless liquid which is about one- 

 half heavier than water. This liquid boils at a temperature of 8^ 0. 

 below zero. I would suggest that it might prove profitable both to sugar 

 manufacturer and chemist to prepare this liquid oxide at a central fac- 

 tory and ship it in suitable iron vessels to the sugar works. In this 

 way the sugar-maker could always have at hand ani under complete 

 <jontrol a pure article of sulphurous dioxide. ^ 



The antiseptic properties of this body are even more marked than its 

 bleaching powers. In a substance so prone to fermentation as cane 

 and beet juice such a preserving agent is of the utmost importance. 

 Dilute cane juices saturated with the gas or a bisulphite may be kept, 

 for days and even years unfermented. 



APPLICATION; 



The gas may be applied directly to the juice — 



(1.) By conducting it into the vessel containing the juice and allow- 

 ing it to be absorbed. 

 16435 N s 6 



