Did Russia use 'chemical weapons' in Ukraine?

The us department of state alleged that Russia had used chemical weapons against the Ukrainian army, and this was the reason to impose additional sanctions against Russia. Interestingly, last week, Russia levelled similar charges against Ukraine at the organization for the prohibition of chemical weapons' conference. Who's using chemical weapons against the other? WION's Shivan Chanana discusses with Dr. Gilbert Doctorow, historian/author/political commentator from Brussels.