A good question and not just for Microphen but all 2 part developers such as Xtol. We could do with a list available somewhere that gave us the answers but we really need a few people who have done what you have just done and can state there was no problem. Nobody may know and a belt and braces approach says that it is worthwhile contacting Ilford anyway.
I have yet to mix my Microphen and if this is sometime soon this thread and your unfortunate experience may help ensure I do not do the same but it would be nice to know
If you dissolved part B in less water than the full amount (to make 1L?) could you try dissolving part A in the balance of the water? And then combining both lots.
It might be that parts A and B are separate for storage rather than for mixing reasons (I don't know). At least there's no metol in it (doesn't dissolve in high sulphite solutions).
If everything has dissolved now, my guess is that it will be ok.
Your negatives will now come out backwards!
If I understand these things correctly, in most cases the reason for mixing things in the order suggested is that some things don't dissolve very well unless you use that order.
Did you later put in the part A, and did it all dissolve?
If I were you, I would contact Ilford/Harman using their contact form on their website and ask the question. You could also "Start a Conversation" here on Photrio with Harman Tech Service and direct them to this thread.
Hi Ajuk,
The problem is in solubility as Matt has already suggested. The developing agents in Part A can be difficult to dissolve after the salts in Part B. Keep it warm at around 40ºC/104ºF and stir lots. If you can get all the Part A to dissolve then you've got away with it!