40 ON THE PKEPARATION OF SODA AND CHLOKINE. 



perchloride of iron. Air having still access, the perchloride of 

 iron is resolved into peroxide of iron and chlorine gas, which 

 latter escapes, and may be recognized by its odor as soon as the 

 evolution of sulphurous acid has ceased. Assuming this expla- 

 nation to be correct, it occurred to me that chlorine might be 

 produced on a large scale by taking advantage of the reactions 

 ■which occur towards the end of the process above described, and 

 by substituting common green vitriol (calcined) for the sulphate 

 of peroxide of iron formed by the reactions just mentioned. 



I found however on calcining a,mixture of four parts of calcined 

 green vitriol (the formula of which may be regarded as Fe 2 3 , 

 2 SO 3 ) and three parts of common salt, in a muffle furnace, at a 

 moderate red heat, that these substances fused together, and evolved, 

 Instead of pure chlorine, a mixture of this gas with vapors 

 of perchloride of iron. I then prepared perchloride of iron by 

 heating together calcined green vitriol and chloride of calcium 

 over a spirit-lamp. Tn this reaction the materials did not fuse 

 together, and the pfrchloride of iron sublimed from the mixture 

 was decomposed at a gentle heat in the muffle into chlorine and 

 peroxide of iron. It was also decomposed when heated with per- 

 oxide of manganese over a spirit-lamp, pure chlorine being evolved. 

 On heating a mixture of calcined green vitriol and common salt 

 in the same way, it fused, but gave no sublimate, nor was there 

 any chlorine evolved on heating the same mixture with peroxide 

 of manganese. On the other hand, a mixture of calcined green 

 vitriol, chloride of calcium, and peroxide of manganese heated 

 over a spirit-lamp did not fuse nor agglutinate, and gave off 

 chlorine abundantly. From these experiments it seemed essenti- 

 al in order to the production of chlorine from calcined green 

 vitriol and common salt, that these materials should be kept in a loose 

 and porous condition, in which state the oxygen of the atmosphere 

 might more readily permeate the mass. I accordingly added to 

 the mixture of four parts of calcined green vitriol and three parts 

 of common salt, an equal weight of peroxide of iron, and heated 

 the mixture in the muffle. The fusion of the materials was thus 

 prevented, and an abundant evolution of pure chlorine took place. 

 On continuing the calcination until chlorine was no longer evolv- 

 ed, I found that the residue consisted almost exclusively of sul- 

 phate of soda and peroxide of iron. The solution obtained by 

 treating it with hot water contained no iron. I then took 474 

 grains (3 equivalents) of calcined green vitriol, 351 grains (6 eq.) 



