Is it possible to recognise sodium ions without using flame?

Jul 26, 2017

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

Explanation:

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

Put 1 small drop of conc. ${\text{H"_2"SO}}_{4}$ in the cavity of a microscope slide.

Add 1 very small particle (max. ${\text{1 mm}}^{3}$) 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 ${\text{HNO}}_{3}$.

The reagent is now ready to be used.

Test for $\text{Na"^"+}$

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, $\text{Na"^"+}$ quickly forms needles of the insoluble salt, $\text{3Na"_2"SO"_4·"2Bi"_2("SO"_4)_3·2"H"_2"O}$.