$\mathrm{CO}_3^{2-}$ and $\mathrm{H}_2 \mathrm{CO}_3$

$\quad \mathrm{H}_2 \mathrm{CO}_3$ and $\mathrm{CO}_2$

$\quad \mathrm{CO}_2$ and $\mathrm{H}_2 \mathrm{CO}_3$

$\quad \mathrm{H}_2 \mathrm{CO}_3$ and $\mathrm{CO}_3^{2-}$

$\left[\mathrm{Co}\left(\mathrm{NH}_3\right)_6\right]^{3+}$

$\mathrm{Cr}(\mathrm{CO})_6$

$\left[\mathrm{Zn}\left(\mathrm{NH}_3\right)_4\right]^{2+}$

$\left[\mathrm{Cu}\left(\mathrm{NH}_3\right)_4\right]^{2+}$

Iron chromate

Vanadium pentoxide

Ni metal

Traces of acid or alkali

Potassium cyanide

Sodium nitrite

Potassium nitrite

Silver nitrite