Maybe it's just luck, but I have a properly calibrated pH meter, and it always reads pretty much 5.2 when I use the stabilizer. Can you give references for the articles you read saying that it doesn't/shouldn't work?
It's not that I have any references to give. It's that yours is the first report I have ever seen of it working properly by someone using a pH meter and so I'm very interested in the conditions under which it did work for you, what your water chemistry is and what your grist composition is. Also, the phrase "I have a properly calibrated pH meter" is attention getting. There may be nothing to it if that means "I have a functioning meter which I calibrate before each use using fresh buffers." but as it wasn't worded that way I have to ask if that is what you meant to say. If it is, I apologize but there are those who think that the little pouches of buffer that come with the $60 meters are used to calibrate them after which they are set.
There are also no references for the statements I made about the theoretical aspects or experiments. Those were done by me. The MSDS for 5.2 says it's a mixture of phosphate buffers. If you put it in DI water it comes to pH 5.7, appreciably different from 5.2. If it's a phosphate buffer at a particular pH it is possible to calculate the ratio of monbasic to dibasic salt. A quick check for potassium shows that there is none (or a trace amount) so both salts must be sodium salts. Given that you know the ratio of monobasic to dibasic and that it is a sodium salt you can figure how much sodium should be in a solution of a given strength. Measurement of the sodium content such a solution gives an answer close to the calculated one. Thus we think we know the composition. I say "think" because there could be other ingredients in there but they are not listed on the MSDS.
So why is it a 5.7 phosphate buffer? Don't really know but my surmise is that they are relying on the reduction in pH which is typically around 0.3 in going from room to kettle temperature in order to be able to claim it's a 5.2 buffer. Of course they never really claim it will get you to 5.2 - that's just the name of the product. Anyway the pH of a phosphate buffer doesn't shift that much with temperature e.g. 7.02 to 6.97 in going from 20 °C to 60°C for a pH 7 buffer used for pH meter cal. The other surmise is that it is a pH 5.7 buffer when mixed with DI water but a pH 5.2 buffer when mixed with the (mostly) monobasic phosphate in malt.
As any freshman chemistry student will tell you buffering capacity falls off very quickly as you move away from pH value close to one of the pK's of the underlying acid. Buffers are not designed for pH values more than 1 pH unit from the closest pK. The closest pK of phosphoric acid is 7.21. pH 5.2 is 2 whole units away from that and 5.7 is 1.2 units away from that. We would not, therefore, expect much buffering capacity from a 5.7 phosphate buffer. Citric acid with its second pK = 4.77 would be a better choice.
So much for theory. In laboratory experiments with Maris Otter malt I found that a nominal water/malt ratio mash, at pH 5.7 with distilled water and 5.93 with my well water (alkalinity about 80) were brought to, respectively, 5.68 and 5.79 with the product at the recommended dose. At quadruple the nominal dose the DI mash pH came to 5.66 and the well water mash to 5.74. IOW, as expected, this buffer can't overcome the combined buffering capacities of the malt let alone the additional capacity of the water. My limited experiments can hardly be considered a full investigation but the implications of the tests I did run are pretty plain. Coupled with the similar observations of others the conclusions are that the stuff isn't quite up to the implied claims. That's why I'm so interested in what you found.
Note: in the mash experiments the ground malt was placed in stainless beakers which were in a water bath at 150 °F. After adding the 5.2 and allowing things to stand for a few minutes samples of the mash were removed to room temperature where the pH was measure with a laboratory pH meter which had been calibrated with fresh buffers just prior to the commencement of the measurements.
