I gave up on the recommended solution because it never worked well for me. I have used Heico Permawash at the standard dilution recommended on the bottle for washing film, it works very well for me, no problems mixing, clears the negative both more quickly and more effectively, and I haven't had any problems with Polaroid 55 negatives being more prone to damage. This is a solution that has been recommended on a number of threads on APUG and elsewhere. If you are concerned about experimenting with it on a really important negative, just shoot a test negative and give it a try.
Doug Webb