The second important method for producing soda ash is Solvisu method, or ammonia-soda method, which was patented by Belgian chemist Solvi (1838 ~ 1922) in 1862. The raw materials of ammonia-alkali process are cheap, and the by-products ammonia and carbon dioxide can be recycled and produced continuously. The product soda ash is of high purity-called "soda ash" at this time, with high yield and quality and low cost, so the Lubran process is gradually eliminated. 1873, the soda ash produced by Solvi company won the honorary prize of pure quality in Vienna International Expo. By the 1920s, the ammonia-alkali method had completely replaced the Lubran method.
However, it is precisely because ammonia-alkali method has so many advantages that this technology is strictly controlled by manufacturers and no leakage is allowed. British Bunemen Company used the patent of ammonia-alkali process to start mass production of soda ash (with an annual output of 200,000 tons) from the end of 19, and thus made a lot of money.