Hydrosulphite, formation

Hydrogen peroxide, 21. Hydrosulphite, formation of, 85, Hydroxylamine, formation of, 82. 

Titanous chloride also reduces sulphurous acid or sodium hydrogen sulphite solution with formation of an orange-yellow solution of hydro-sulphurous acid,5 from which sodium hydrosulphite is obtainable by further treatment with sodium hydroxide solution ... 

In the presence of alkali, hydrosulphites react with alkali polysulphides with the formation of sulphite and sulphide ... 

Aqueous solutions of hydrosulphites become orange-yellow on acidification and the presence of sulphur dioxide is soon evident. The yellow colour is not due to colloidal sulphur, nor, since its salts are colourless, would it be expected that tlie free acid should be yellow, unless there is some change in constitution. It has therefore been suggested 4 that the decomposition on acidification involves the formation of a coloured isomeride of the type (H0)2S.S02 by co-ordination of a molecule of sulphur dioxide with the sulphur atom of sulphoxylic acid. The decomposition may proceed thus ... 

Auction if the Hydrosulphite B X is insufficiently used (formation of ferrous sulphide). 

When mildly reduced, for example with sodium sulphide or hydrosulphite or with ferrous sulphate, picric acid is converted into picramic acid, a very useful intermediate in the dyestuffs industry and a starting material for the preparation of dinitrodiazophenol, a primary explosive (Vol. III). Stronger reduction may lead to the formation of triaminophenol. 

The reduction of quinoline with either lithium or sodium in liquid ammonia produces only 1,4-dihydroquinoline . Formation of 1,2-dihydroisoquinolines was observed in the reduction of quaternary isoquinoline salts with sodium hydrosulphite ", lithium aluminium hydride " , NaBH4 , dialkylaluminohydrides or on treatment with a Grignard reagent . 

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