Verification of carbonate and sulphate barium hydroxide

Chemicals needed

distilled water

bariumhydroxide, octahydrate C    R 20/22-34    S 26-36/37/38-45

sodium carbonate

sodium sulfate

hydrochloric acid 7%

Equipment necessary

2 test tubes

Test procedure

• Caution, barium compounds are toxic! Safety goggles!
• One adds into each test tube a small spatula-tipful of barium hydroxide and dissolves this in about 2 ml of water.
• One adds to the first test tube a little sodium carbonate and to the second a little sodium sulfate and slightly sway them back and forth. In both cases a turbid white precipitation occurs.
• One adds to both mixtures about 0.5 ml of diluted hydrochloric acid. The carbonate precipitation is dissolved immediately, in contrast the sulfate precipitation remains.
  

Disposal

• The residues are to be disposed of as heavy metal waste.

Elucidation

A poorly soluble barium carbonate is formed, which then precipitates. The slightly acidic carbonate can be dislodged as carbon dioxide, not however the strongly acidic sulfate.

Photos

Precipitation of barium carbonate (left) and barium sulfate (right)

The carbonate precipitation is dissolved by acidifying.

Literature

Experiment based on own considerations. Alternatively one can dissole carbonate and sulfate in water and then add barium hydroxide solution.