ON THE PREPARATION OF SODA AND CHLORINE. 47 



possible, to the action of the air and of moisture. It is placed on 

 a perforated wooden floor covered with cloth, and supported over 

 an impervious bottom of clay or other material, so inclined and 

 arranged that the solution obtained in lixiviating the mass may 

 be conveniently collected for further treatment. The moist sul- 

 phuret rapidly oxidizes, and passing through various intermediate 

 stages of oxidation, it ultimately becomes very rich in sulphate of 

 iron. It must never be allowed to oxidize so rapidly as to enter 

 into combustion, because in that case sulphurous acid is produced, 

 which would escape as gas, and be lost. This tendency to oxidize 

 too rapidly may be counteracted by keeping the material moist. 

 When a sufficient quantity of sulphate of iron has been formed in 

 the mass, hot water is poured over the whole surface. This per- 

 colating through dissolves the sulphate, and falling on the im- 

 pervious floor beneath, flows into channels prepared for it, and is 

 finally collected in a large reservoir. The solution thus obtained 

 is concentrated in boilers of the same description as those used in 

 copperas works, and crystals of green vitriol are obtained in the 

 manner usually adopted in the same establishments. The exposure 

 and lixiviation of the sulphuret is continued and repeated until a 

 residue is left consisting exclusively of peroxide of iron, and con- 

 taining no sulphur. The green vitriol obtained as above described, 

 is used in the first part of the soda process and the residue of per- 

 oxide of iron, if sufficiently pure, may also be used in that operation. 

 This production of sulphate of iron, and of the residue of peroxide 

 of iron, may be called the third and last part of the process. 



Having thus to some extent described the new method of pre- 

 paring chlorine and carbonate of soda, I proceed to advert to the 

 advantages which it possesses over the ordinary process. The manu-. 

 facture of bleaching powder and soda, as at present pursued, com- 

 prises the following operations ; 1st. The manufacture of sulphur- 

 ic acid from iron pyrites or sulphur, by the action of nitrous acid 

 on the sulphurous acid and atmospheric air admitted into the lead- 

 en chamber, which nitrous acid is produced by the action of 

 sulphuric acid on nitrate of soda; 2nd. The production of sulph- 

 ate of soda and muriatic acid by the action of sulphuric acid on 

 common salt ; 3rd. The production of chlorine (and of bleaching 

 powder,) by the action of muriatic acid upon the peroxide of 

 manganese, in which process however only one half of the chlorine 

 contained in the muriatic acid is evolved in the form of gas, 

 the other half combining with manganese and forming- with 



