6. Strontium

1. Ammonium carbonate

$Sr^{2+}$ $+$ $CO_3^{2-}$ $\longrightarrow$ $SrCO_3$ - White precipitate - Soluble in $HCl$ - Soluble in acetic acid

2. Potassium bichromate

- There is barely precipitation in a buffered medium at pH = 5 - $K_2CrO_4$ precipitates $Sr^{2+}$, but also $Ba^{2+}$

3. Dilute sulfuric acid

$Sr^{2+}$ $+$ $SO_4^{2-}$ $\longrightarrow$ $SrSO_4$ - White precipitate - Slow reaction - $SO_4^{2-}$ ions must be abundant

4. Calcium sulfate

$Sr^{2+}$ $+$ $SO_4^{2-}$ $\longrightarrow$ $SrSO_4$ - White precipitate - $CaSO_4$ is poorly soluble in water (0.2 g in 100 mL). Since the solubility of strontium sulfate is very small, the precipitation takes place anyway, but it is slow and accelerated by heat.

5. Potassium hexacyanoferrate(II) ($K_4Fe(CN)_6$)

- no precipitate, even by heat