314 



THE ALUMNI JOURNAL. 



and treated by the Weldon-Pechiney pro- 

 cess. 



CHI.ORINE IN THE AMMONIA SODA 

 PROCESS. 



I have repeatedly referred during this 

 brief history to the great change which 

 has been brought about in the position 

 of chlorine manufacture by the develop- 

 ment of the ammonia soda process, and 

 have pointed out that the muriatic acid 

 which for a long time was the bye-pro- 

 duct of the Le Blanc process, without 

 value, thereby became gradually its main 

 and most valuable product, while the 

 alkali became its bye-product. 



I have told you now, very early in the 

 history of this process, Mr. Solvay and 

 Mr. Weldon proposed means to provide 

 for this contingency, and how Mr. Wel- 

 don continued to improve these means 

 until the time of his death. Mr. Solvay, 

 on his part, also followed up the subject 

 with that tenacity and sincerity of pur- 

 pose which distinguishes him; his en- 

 deavors being mainly directed to produc- 

 ing chlorine direct from the chloride of 

 calcium running away from his works by 

 mixing it with clay and passing air 

 through the mixture at very high temper- 

 atures, thus producing chlorine and a 

 silicate of calcium, which could be util- 

 ized in cement-making. The very high 

 temperatures required prevented, how- 

 ever, this process from becoming a prac- 

 tical success. 



I have already told you what a com- 

 plicated series of operations Dr. Pick has 

 lately resorted to in order to obtain the 

 chlorine from this chloride of calcium. 

 Yet the problem of obtaining chlorine as 

 a bye-product of the ammonia soda pro- 

 cess presents itself as a very simple one. 



This process produces a precipitate of 

 bicarbonate of soda and a solution of 

 chloride of ammonium by treating nat- 

 ural brine, or an artificially-made solution 



of salt, in which a certain amount of am" 

 monia has been dissolved, with carbonic 

 acid. In their original patent of 1838, 

 Messrs. Dyar and Hemming proposed to 

 evaporate this solution ol ammonium 

 chloride, and to distil the resulting dry 

 product with lime to recover the ammo" 

 nia. Now, all that seemed to be neces- 

 sary to obtain the chlorine from this 

 ammonium chloride was to substitute 

 another oxide for lime in the distillation 

 process, which would liberate the am- 

 monia and form a chloride which, on 

 treatment with atmospheric air, would 

 give off its chlorine and reproduce the 

 original oxide. The whole of the reac- 

 tions for producing carbonate of soda and 

 bleaching powder from salt would thus 

 be reduced to their simplest possible 

 form ; the solution of salt, as we obtain 

 it in the form of brine direct from the 

 soil, would be treated with ammonia and 

 carbonic acid to produce bicarbonate, and 

 subsequently monocarbonate of soda ; 

 the limestone used for producing the car- 

 bonic acid would yield the lime required 

 for absorbing the chlorine, and produce 

 bleaching powder instead of being run 

 into the rivers in combination with chlor- 

 ine in the useless form of chloride of cal- 

 cium ; and both the ammonia (used as 

 an intermediary in the production of 

 soda) and the metallic oxide (used as an 

 intermediary in the production of chlor- 

 ine), would be continously recovered. 



The realization of this fascinating prob- 

 lem has occupied me for a great many 

 years. In the laboratory I obtained soon 

 almost theoretical results. A very large 

 number of oxides and even of salts of 

 weak acids were found to decompose am- 

 monium chloride in the desired way ; but 

 the best results (as was to be clearly an- 

 ticipated from thermo-chemical data) 

 were given by oxide of nickel. 



( To be C07itinued. ) 



