Estimations based on the Use of Titanous Salts

This energetic reducing agent can be maintained at constant strength in aqueous hydrochloric acid solution for a reasonable period. It is advisable, however, to re-standardise it after 24 hours standing. It serves for the reduction of aromatic nitro compounds, some nitroso bodies, many azo dyes, and of nearly all the dyes which yield leuco-compounds. It is easily standardised against a ferric salt—say ferric alum—using potassium thiocyanate as indicator. From the equations — 

Preparation and Storage of Titanous Chloride Solution- for Analysis.— 

of the commercial titanous chloride solution (20%) are boiled with 100 c.cs. of cone, hy- 

Standardisation.—3-5 gms. of pure ferrous ammonium sulphate are dissolved in distilled water, 100 c.cs. of 5N sulphuric acid added, and the whole made up to 250 c.cs. 25 c.cs. of this are oxidised with potassium 

A solution of iron alum, containing about 14 gms. per litre, and acidified with sulphuric acid until the solution assumes a pale straw colour, is prepared. By titrating 25 c.cs. of this with titanous chloride, using potassium thiocyanate as indicator, its strength is determined, and as it will retain its strength for a long period, this alum solution may be used in all subsequent cases for standardising the titanous chloride solution. 

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