TECHNOLOGY. 597 



These crystals were found, on examination, to have the 

 same chemical composition, the same hardness, the same spe- 

 cific gravity, and the same crystalline form as the natural 

 ruby and sapphire, and were, in fact, not to be distinguished 

 therefrom. 



At the same meeting of the French Academy at which 

 Messrs. Fremy and Feil described their process, M. Monnier 

 stated that he had succeeded in obtaining artificial opals by 

 cautiously pouring oxalic acid upon a sirupy solution of sil- 

 icate of sodn. 



THE AMMONIA PROCESS OF SODA MANUFACTURE. 



In the llecord for 1873 Ave noted that much interest 

 had. been attracted at the Vienna Exhibition by the dem- 

 onstration of the fact by M. Solvay, a Belgian manufact- 

 urer, that soda could be successfully produced upon the 

 commercial scale in competition with the time-honored proc- 

 ess of Leblanc. The distinguished chemists Hofmann and 

 R. Wagner, in their reports on the chemical industries of 

 that exhibition, were so favorably impressed with the em- 

 inent merits of the ammonia process that they coincided in 

 the opinion that it was destined in time to entirely supersede 

 the process of Leblanc, which for more than half a century 

 had held its own against all rivals. At the time of the Vi- 

 enna Exhibition the yearly production of soda by M. Solvay 

 amounted to about 8,000,000 pounds. In the five years that 

 have elapsed since that time the annual production of soda 

 by the ammonia process has risen to 88,000,000 pounds, one 

 establishment (that of Verangeville-Dombasle) producing one 

 half of this total. The soda produced by the ammonia proc- 

 ess is said to be almost chemically pure, being almost per- 

 fectly free of sulphate of soda and iron. This fact, taken in 

 connection with its cheapness, renders it not only well adapt- 

 ed for all the industrial uses to which Leblanc soda is put, 

 but for special uses glass- making, for instance makes it 

 of peculiar value. From the foregoing resume, showing the 

 steady growth of the ammonia-soda process, and its present 

 important position, it would appear as if the prediction 

 ventured by Messrs. Hofmann and Wagner in 1S73, regard- 

 ing its future importance, was in course of rapid realiza- 

 tion. 



