[Caustikola]

I usually prepare HCl by the dissolution of Cl2 in water and then leaving the HOCl formed to decompose in uv. Pls what is the maximum concentration of HCl that can be obtained via this process?

[Arkcon]

Well, we'll have to start with the maximum solubility of Cl2 and HOCl in the water at the highest temperature its likely to experience under the UV source.  You might be able to find an online resource for that fact.  Then, we can use stoichiometry to follow the reactions, which would be a fun little exercise.  Off hand I'd say ... not very concentrated.  Certainly much less than the 33-35% HCl I can buy from the hardware store for cleaning tile and masonry.

[marquis]

We could generate HOCl at about 1500 ppm by bubbling Cl2 through water.  You might be able to get a little higher than this (say 3000 ppm), but you will have a number of issues.  This level could only be generated with a scrubber and other safety measures.

You can get commercial grades of bleach at 15%, if needed.  Do not plan on storing it in this concentration for long periods of time.  It will degrade in month or two to much lower concentrations.

Good luck.