What acid is identified by barium chloride

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Detection of barium

Spectroscopic evidence

Barium ions are precipitated in the ammonium carbonate group of the separation duct alongside calcium and strontium.

Barium shows a pale green flame color (several green lines, of which those at 524.2 and 513.9 are particularly characteristic).

Precipitation as sulfate

Barium forms a sparingly soluble sulfate, which does not dissolve again even in acid. Strontium and calcium also form sparingly soluble sulfates, but barium sulfate has the smallest solubility product of the three sulfate salts. As a result, more can precipitate from a saturated solution with barium ions, recognizable by the turbidity of the reaction solution.

Precipitation with dichromate

Barium forms a poorly soluble yellow precipitate with chromate ions. The dependence of this precipitation on this precipitation allows strontium to be separated from barium.

Note
While barium at a value of 3 (acetic acid solution) is quantitatively precipitated as chromate, strontium and calcium do not precipitate.

This can be deduced from a consideration of the solubility products and the equilibrium constants for the chromate-dichromate equilibrium.

It can be seen that the higher the value of the solution, the higher the chromate concentration. In other words, the concentration of the chromate ions can be adjusted via the value.

The following solubility products apply to stontium and barium chromate:

Computational derivation

From the mathematical derivation it can be seen that practically only the solubility product is exceeded, but not for. Or to put it another way: The concentration required to precipitate is much too high for a precipitate to form under the above conditions.

At = 3 and a 0.1 molar solution, only a concentration sufficient to precipitate.

However, under changed conditions - neutral or basic at higher concentrations - it can be precipitated and can then be identified by its characteristic crystal shape (broom-like crystal clusters).