Abstract: The process for producing a clear solution of alkali metal silicate having an SiO.sub.2 /alkali metal oxide weight ratio of 2.5 or less which comprises passing an aqueous solution of an alkali metal hydroxide through a bed of crystallized silica having an average particle size of between about 0.1 mm and 2 mm formed in the bottom of a vertical tubular reactor without mechanical agitation, said silica and alkali metal hydroxide being fed from the top of the reactor, and recovering the resulting clear solution of alkali metal silicate from the bottom of the reactor.

Abstract: Processes for treating nitric effluents from plants so that a non-polluting stream is obtained and nitric values are recovered, which processes comprise acidifying nitric effluent, liquid-liquid extraction of the acidified effluent with an extraction agent comprising a neutral phosphoric ester and at least one long-chain alkylamine, and re-extraction of the loaded extraction agent with ammonia, thereby regenerating the extraction agent and providing ammonium nitrate, while at the same time providing a substantially nitric-free effluent.