testing the concentration of Ammonia


I have made up solutions of Ammonia solution but now im questioning their correct concentrations. CLEAPPS says that the concentration of ammonia decreases with age and we have some pretty old bottles of ammonia in the cupboard! do you do a titration with sulphuric acid?
Its faster to just make a fresh batch. With how volatile ammonia is, by the time you finished your titration, the concentration would have changed...
Thanks. I'm just questioning how strong the original bottle of ammonia is to start with as they are pretty old.

What was the original concentration?
The hazcard for ammonia solution just states to dilute to <0.5M then down the sink. Since you don't know the original conc I would honestly (in a fume cupboard) just chuck it in a large container full of water then down the sink.
I would make up a what you think is a 1M solution of ammonia from your old stock bottle and then titrate it with 1M HCl.
At least that will give you a rough idea of the strength of your stock bottle.
Google suggests methyl orange as the indicator.