Hi Goron
I am not familiar with the finer points of Hydramaster's Cleaning Solutions, so cannot comment on them. It would be wise though, especially with oriental rugs, to use only Woolsafe Approved products.
In many cases, using an acidic rinse may not be the best route to take. Yes, this rinse will leave a carpet in acidic state, but quite often it is to correct a pH imbablance. Being safe with wool isn't just about pH, it's also about Alkalinity which is not quite the same as pH. Most Woolsafe Approved solutions are quite close to neutral pH and are typically, but not always in the pH5.5 to 8.0 range. Sometimes you can have an unbuffered pH10.0 which is kinder than a buffered pH9.0.
So, in a nutshell, especially with your oriental, play safe and stick to Woolsafe Approved Solutions and TEST, TEST, TEST every single colour with every product you will use. And make yourself an Easter Wish to attend one of the excellent Woolsafe Training Courses this year.
Safe and happy cleaning

Ken