reagent

Barium nitrate, added to a solution acidified with nitric acid, is the group reagent.

Silver nitrate, added to a solution acidified with nitric acid, is the group reagent.

Barium nitrate, used with a neutral solution, is the group reagent in the absence of metal ions other than the alkali metal ions.

Do this by boiling some of the sample in water, and when cool adding a drop or two of iodin reagent.

When a precipitate forms with the above reagent, it should settle immediately and leave a clear and almost colorless liquid.