Is it possible to recognise sodium ions without using flame?

1 Answer
Jul 26, 2017

Yes, it is possible to test for sodium ions without using a flame.


The test is based on the formation of an insoluble sodium salt.

Put 1 small drop of conc. #"H"_2"SO"_4# in the cavity of a microscope slide.

Add 1 very small particle (max. #"1 mm"^3#) of #"Bi"("NO"_3)_3# to the drop.

Stir briskly for 1 to 2 min with a glass rod [#"Bi"("NO"_3)_3# dissolves very slowly].

When the solution is saturated, the acidic drop becomes white and stiff and swells visibly.

Add 1 drop of deionized water and stir vigorously.

When the white salt is dissolved the solution should be colourless or perhaps opalescent.

Add 1 drop of 2 mol/L #"HNO"_3#.

The reagent is now ready to be used.

Test for #"Na"^"+"#

Add 1 drop of the reagent solution to a previously dried test drop on an object slide.

Observe the reaction products under the microscope at a magnification of about 100X.

Usually, #"Na"^"+"# quickly forms needles of the insoluble salt, #"3Na"_2"SO"_4·"2Bi"_2("SO"_4)_3·2"H"_2"O"#.