Hi Duncan,
I have been making my own MMS and activators for a while now and I get quite a range of reactions even out of the same two bottles. Sometimes it smokes, sometimes it doesn't. Sometimes it's more clear, other times you might describe it as cloudy. Doesn't matter whether it is a fresh made batch of MMS or has been in PET bottles for months. The only important thing in my mind is that it is yellowish possibly tending to brownish and it smells right.
The sodium chlorite Jim recommends is technical grade 80% which leaves plenty of room for variability, but it is has not proved harmful in experience. I just made a new batch of MMS and I am putting some in glass bottles, PET bottles and HDPE bottles and I will watch what happens over several months. But really none of these are perfect solutions. Some chemicals react strongly with glass even, and glass itself is variable because it is made from natural materials. As a matter of fact, I put some dry sodium chlorite flakes in some mason jars for several months and the jars now have stains I have not been able to remove; it may have reacted with the glass because I have never seen stains like this before.
I think the PET, HDPE and glass all work fine for MMS. Jim says he has bottles (PET I assume) that are 4 yrs old and still work fine. Whatever impurities and reactions are present are not enough to affect the results Jim has been able to obtain, or he would tell us.
Now that I am using HCl primarily for my MMS I am getting smoke and bubbles with every reaction. I react quite a bit of MMS because of my bag treatments using 1/2 tsp. each time, plus the oral doses. In my experience there is a great deal of variability in these reactions and the most important thing is that it is yellow possibly tending toward brownish and smells right.
This is my opinion based on my experience.
Michael