42 ON THE PREPARATION OF SODA AND CHLORINE. 



After this I performed two additional experiments with the 

 following proportions of materials : — 



I. II. 



Calcined green vitriol. ..316. . .450 



Common salt 234. . .351 



Peroxide of iron 78 .... 78 



The muffle was kept at a faint red heat, and in both cases 

 chlorine was abundantly evolved. Finally I found that it was 

 even possible to calcine 316 parts of calcined green vitriol and 

 234 parts of common salt, without any admixture of peroxide of 

 iron, and to obtain an abundant disengagement of chlorine. In 

 this case however the muffle was not allowed to attain even the 

 faintest redness. Even at this low temperature the materials 

 sintered together slightly. I had thus by this series of experi- 

 ments ascertained the exact conditions most favorable to the 

 disengagement of chlorine from a mixture of calcined green vit- 

 riol and common salt, and proved that the explanation given above 

 of the production of chlorine in calcining iron pyrites with com- 

 mon salt was the correct one. In the course of these experiments 

 I was also led to expose chloride of manganese to a moderate 

 red heat in the muffle, in presence of a current of air, as in the 

 above trials. I found that that substance in an impure state, 

 (prepared by evaporating to dryness the residue from the pre- 

 paration of chlorine from peroxide of manganese and hydrochlo- 

 ric acid,) was in this way converted into an oxide of manganese 

 of a higher degree of oxidation than the protoxide, with abun- 

 dant disengagement of chlorine. The decomposition was easily 

 effected, still it seemed as if peroxide of iron, or manganese, when 

 mixed with the impure chloride of manganese, accelerated the 

 evolution of the chlorine. The residue from the decomposition 

 of the impure chloride of manganese, if exposed in the muffle 

 until the evolution of chlorine was no longer observable, yielded 

 chlorine when heated with hydrochloric acid, but none when heated 

 with sulphuric acid. This last reaction proved that no un- 

 decomposed chloride of manganese was left in the calcined residue. 

 The residue from the production of chlorine from calcined 

 green vitriol and common salt, consisting of a mixture of sul- 

 phate of soda and peroxide of iron, on being mixed with pow- 

 dered coal or charcoal, and ignited, fuses readily, and the resulting 

 product, when treated with water, affords an alkaline solution, 



