How to pass the portal language with the URL

Dear experts,

We are trying to call the SAP Enterprise Portal (Online Catalogue) from SAP ERP (ECC6) with an URL that looks somehting like this:

http://xxx.com/irj/portal?j_user=xx&j_password=xx

This works fine, however we would like to add the language as a parameter, something like &language=IT but this doesn't work. I've tried multiple paramaters but none of them brought any success.

The only half-valuable parameter we found is ume.logon.locale which is only considered on the logon screen, though.

Does anybody know which parameter I need to use? Does the SAP Enterprise Portal accept language settings comming from the URL?

Thanks a lot & regards,

Pascal Thalmann