chlorine formed in hydrochloric acid Is it plausible that free chlorine could be formed in concentrated hydrochloric acid.

The background to this is that I have bought some 30% HCl to remove calcium carbonate scale from a reverse osmosis water purifier. The latest batch of HCl seems to have a very slight yellowish tint which I had not noticed on previous occasions. Having used some of this acid I find that the performance of the membrane seems to have deteriorated (these membranes are notably sensitive to hypochlorite).

Could some factor (perhaps exposure to direct sunlight) be responsible?

Is there a way that I could detect the presence of dissolved chlorine?

Can anyone suggest an alternative explanation?

Thanks,
Chris.
You could buy the chlorine test strips from a pool supply store to test for hypochlorite. You may need to neutralize the acid before testing, so ask if the test is accurate in a strong acidic solution.