Aquamira A+B ratio critical?

One is going to be the limiting reagent in chemistry talk, so I'm guessing the volumes needed err on the worst case scenario after the manufacturers testing. I'd still keep the relative ratios the same if only to keep A and B bottles balanced. Now I'm not going to worry whether I'm treating a liter or 1010mL (letting that chemistry freak flag fly!!!)

OK, part B is the "activator" so is that the limiting reagent?

Therefore err on the side of a bit too much part B?

I use epoxy glues quite frequently and the bottles never end up with the same amounts of resin and hardener…

Clearly I'm no Walter White.

AM calls for a 50/50 mix of parts A and B; 7 drops of each per liter of water treated. The size of the drops doesn't matter as long as they are the same size for both parts.

What does matter is how much of that mix you use per volume of water treated.

AM claims you need the full 14 drops per liter, using their dropper bottles.

BPL tests have shown that when using mini-dropper bottles (like you are), the drop sizes from those bottles are smaller (therefore less volume per drop) than those from the AM bottles. Therefore, you need MORE drops per liter than you would with the standard AM bottles.

That said, disinfection follows an essentially linear curve of contact time vs. concentration. The stronger the concentration, the shorter the contact time required, and vice versa. If you are concerned that your mix is less potent than it should be or that you used less of it than you needed, just increase the contact time.

Example: I put 14 drops of AM into 2 liters instead of one. I now have half the concentration required. Accordingly, I double the regular 30 minute contact time to 60 minutes.

There is also a time/temperature relationship at work. Extremely cold waters also require a longer contact time, even at the correct concentration. Nowhere along the PCT or CT have I ever encountered water I deemed cold enough to do that.

YMMV

Depends on the mini dropper you use as to what size drops they produce from their droppers. Reports are that most commonly sold ones do indeed have smaller dropper sizes, however the sample eye drops dropper I repurposed from my eye Dr. (which looks identical to the purchased ones) have the same sized drops as the original AM bottles.

I know this, because I put aprox 110 drops from the original AM bottle into the dropper to fill it, then got aprox 110 drops back out when I emptied the mini into the main bottle again. I recommend the same test to determine the proper drop ratio for any new bottles used.

Also, I've posted the question before about the practice of premixing, as it is a common practice as you say. The resulting comments from BPL were pretty unanimous that it's an acceptable practice. However, the only evidence anyone can produce, is that either "I haven't got sick", or "He/she does it, so it must be ok". Worthless anecdotes coming from mostly mtn stream drinkers IMO. Now if I were to hear these claims from a bunch of swamp-water drinking midwesterners, I'd be more convinced.

To the contrary, I've read multiple responses from McNett, and have received one of my own from them, stating how the "off-gassing" that occurs once the agents are active renders the solution much less effective, and basically becomes "flat" over an undetermined short period of time.

For me, it's not worth going through all the trouble of treating in the first place, if it's only going to be half as effective, just to save 5 minutes of wait time.

If one deems water purification important, which I do, then IMO it is best to exactly follow the manufacturer's instructions. Given that, I find the drops to be a royal pain in the butt and years ago switched to tablets. I buy them in large quantities when on sale.

Guys,

I appreciate very much the input, but specifically from a chemical standpoint how is potency affected by a slight mismatch in the A:B ratio?

Nick, I agree that if I had to do the liquid mix every time I got water, then that would indeed be a PITA. In hot weather with higher water consumption, that could amount to 5 minutes or more every hour. However, Mike Clelland seems to have maintained his position over the years that you can do a little mix in the morning and you're set for the day. That is incredibly convenient for me because there are plentiful water sources in the nearby areas where I hike so I need carry only a 20-oz Gatorade bottle, so I can fill up and go. I realize this scenario would likely be very different in other environments.

And also the cost per liter is a lot cheaper with the liquid AM.

“However, Mike Clelland seems to have maintained his position over the years that you can do a little mix in the morning and you’re set for the day.”

N=1
His Water = Your Water ??

It is convenient.
Efficacy is questionable. See the last third of the page.

I have emailed McNett on the precision required. I’ll post the response.

Thanks, Greg!

In the meantime, does anyone have any specific (lab-tested?) info about the degradation of potency for those using a pre-mix?

If the gassing-off is prevented by a well-sealed bottle, does the potency remain for a few hours?

The small bottle on the right is a mix I did this morning at 6:30. The only "scientific" observation I can make at this point is "Gee, it still smells very chlorine-y!"

The rate of degradation of the mix is supposedly increased by the presence of light. Dark bottles are recommended for storing the mix. Alternatively, just wrap the bottle in duct tape or electrician's tape and call it good.

McNett has said that as long as the mix is still yellow, it is still effective.

"The only "scientific" observation I can make at this point is "Gee, it still smells very chlorine-y!""

Which indicates it is off gassing. The question is how much, and would it maintain the concentration rquired for efficacy of 4 ppm over a period of several hours? I guess it boils down to personal risk tolerance. Myself, were I in a situation where I felt it necessary to use it in the first place, I'd mix on the spot and wait 5 minutes, but that is just personal risk tolerance talking.

I exchanged emails with McNett regarding the hypothetical acceptability of a "6:7" drop ratio, phrased differently each time, with disclaimers, but basically got the run around, with them saying only "Use as Directed".

It's going to take an off-the-record private conversation to learn anything.

Thanks so much for the effort, Greg, but that is what I suspected.

I do not blame them for staying within very conservative legal and scientific bounds, especially with the work they're putting into getting the EPA to certify the liquid version to have the same efficacy as the tablet version.

In the meantime, the little bottle I mixed up a bit more than 39 hours ago is still a nice yellow color and still has a strong chlorine smell, although (very subjectively!) not quite as strong as before.

About 11:30 this morning I put 9 drops of it into some water I got from a local pond, one with the kind of still, warm water that one suspects would breed a lot of things you wouldn't want to ingest. The water had a yellow/brown tinge to it, with a fair amount of suspicious things floating about, and no doubt a bunch of unseen nasties, but within about an hour of treatment it cleared right up. In a pinch, I'd definitely strain out the bigger chunks and drink it.

This is why I tend to suspect that pre-mixing for a day's use is safe under all but the most ridiculously extreme circumstances – such as drinking feed-lot water – and that a small error in the ratio is probably okay.

But as with most things these days, legal implications prevent a simple answer. Which is why we end up putting more faith in the collective anecdotal experience, which in this case is quite extensive.

At any rate, this has all piqued my interest in finding out about test kits so I may check for myself.

I'd guess we have all done this before and lived. But obviously there is a 1 to 1 molar reaction going on when mixed to create the active big zapper molecules. So very likely if you mix 6 and 7 drops then you get 6 parts of the good stuff (as opposed to 7 if you did the mix as directed), plus 1 part of an added left-over component of A or B that probably doesn't hurt you. So IMO take the smaller number and that is probably the diminished effectiveness, and if you don't puke from the left over A or B then you should be fine.

Unless it is just a PH thing for"activation" – then it could be more of a non-linear effect. Still I think eyeballing it would work in either case

Among other info from McNett:
If a person adds the mixture too early or late, the final concentration of ClO2 in the water can be significantly less than the required 4ppm.

Also, cold water isn’t really a factor:
Water is ready to drink in 15 minutes (or 30 minutes in colder water, although studies show that because of Aquamira’s low pH the treatment time is not significantly impacted by cold temperatures).

Wait Times –

Just to beat this dead horse again, because “30 minutes” is not full disclosure –

“Under worse case scenarios (really cold and turbid water), it could take up to 4 hours to effectively remove Cryptosporidium. Our filters will remove greater than 99.9% of Cryptosporidium and Giardia immediately. That said, it’s a really good idea to use the filters in conjunction with the drops or tabs for quick access to clean and safe drinking water.” [emphasis added]

Because of some regulatory foolishness, in that first sentence McNett can’t/won’t talk about Giardia, also a large tough cyst, which falls into the same treatment category as Crypto.

So for “medium case scenarios” – e.g. 50°F water, bio-filmed crud, … 2 hours for Crypto and Giardia?

Consider the “level of risk” of your water source.
Know what you are dealing with, and how to neutralize it.