282 



THE ALUMNI JOURNAL. 



The hope, however, which Davy ex- 

 pressed in that same historic paper, "that 

 these new views would perhaps facilitate 

 one of the greatest problems in economical 

 chemistry, the decomposition of the muri- 

 ates of soda and potash," was not to be 

 realized so soon. Although it had chang- 

 ed its name, chlorine was still for many 

 years manufactured by heating a mixture 

 of salt, manganese, and sulphuric acid in 

 leaden stills as before. 



CHLORINE AS A BYE-PRODUCT. 



This process leaves a residue consist- 

 ing of sulphate of soda and sulphate of 

 manganese, and for some time attempts 

 were made to recover the sulphate of 

 soda from these residues, and to use it 

 for the manufacture of carbonate of soda 

 by the Le Blanc process. On the other 

 hand, the L,e Blanc process, which had 

 been discovered and put into practice al- 

 most simultaneously with Berthollet's 

 chlorine process, decomposed salt by sul- 

 phuric acid, and sent the muriatic acid 

 evolved into the atmosphere, causing a 

 great nuisance to the neighborhood. 



Naturally, therefore, when Mr. Wil- 

 liam Gossage had succeeded in devising 

 plant for condensing this muriatic acid, 

 the manufacturers of chlorine reverted to 

 the original process of Scheele, and heat- 

 ed manganese with the muriatic acid 

 thus obtained. Since then the manu- 

 facture of chlorine has become a bye- 

 product of the manufacture of soda by 

 by the Le Blanc process, and remained so 

 till very recently. 



For a great many years the muriatic 

 acid was allowed to act upon native ores 

 of manganese in closed vessels of earth- 

 enware or stone, to which heat could be 

 applied, either externally or internally. 

 These native manganese ores, containing 

 only a certain amount of peroxide, con- 

 verted only a certain pecentage of the 

 muriatic acid employed into free chlorine. 



the rest combining with the manganese 

 and iron contained in the ore, and form- 

 ing a brown and very acid solution, 

 which it was a great difficulty for the 

 manufacturer to get rid of. Consequent- 

 ly, many attempts were made to regen- 

 erate peroxide of manganese from these 

 waste liquors, so as to use it over again 

 in the production of chlorine. 



These, however, for a long time re- 

 mained unsuccessful, because the exact 

 conditions for super-oxidizing the pro- 

 toxide of manganese by means of atmos- 

 pheric air were not yet known. 



DUNLOP'S WORK ON CHLORINE. 



Meantime, viz., in 1845, Mr. Dunlop 

 introduced into the works created by his 

 grandfather, Mr. Charles Tennant, at St. 

 Rollox, a new and very interesting meth- 

 od for producing chlorine, which was in 

 a certain measure a return to the process 

 used by the alchemists. 



Indeed, the first part of this process 

 consisted in decomposing a mixture of 

 salt and nitre with oil of vitrol — a reac- 

 tion that had been made use of for so 

 many centuries. The chlorine so obtain- 

 ed is, however, not pure, but a mixture 

 of chlorine with oxides of nitrogen and 

 hydrochloric acid which Mr. Dunlop had 

 to find means to eliminate- 



For separating the nitrous oxides Mr. 



Dunlop, adopted the method introduced 



twenty years before by the great Gay- 



Lussac in connection with vitriol-making 



viz., absorption by sulphuric acid, and 



the nitro-sulphuric acid thus formed he 



also utilized in the same way as that 



obtained from the towers which still bear 



Gay-Lussac's illustrious name, viz., by 



using it in the vitrol process in lieu of 



nitric acid. He then freed his chlorine 



gas from hydrochloric acid by washing 



with water, and so obtained it pure. This 



process possessed two distinct advantages 



(i) it yielded a very much larger amount 



