Ok, I have this expired 500 g lecture bottle of anhydrous HBr (cost 700 Euro). Its expiry date is 2003 but the bottle is almost unused. It would be a shame to dispose of it. The main valve turns and I can see the pin moving but no gas comes out. There must be sufficient corrosion damage in the valve. One suggestion from a rather brave researcher was to freeze the cylinder to condense the HBr and then remove the main valve, clean it/replace it and hey presto problem solved. Sounds suicidal but if anyone has done this successfully or has a safer alternative I am all ears.