During the QC check of one of the products that we make as a company, the product had a $\mathrm{pH}$ of $10.44$ on one $\mathrm{pH}$ meter and $10.20$ on the other. (The product is a liquid, so it's straightforward to immerse $\mathrm{pH}$ probes to take the measurements.)

For QC of the product, it is required to make a $1\%$ solution using demineralised water and to take a $\mathrm{pH}$ reading.

The first $\mathrm{pH}$ meter read $11.72$ for this $1\%$ solution, and the second meter read $11.41$.

How is it possible for the raw product's $\mathrm{pH}$ to be lower than the $1\%$ solution's $\mathrm{pH}$? The product is supposed to be basic and not acidic at all.

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    $\begingroup$ pH is a property of solutions. Bronsted-Lowry bases work by removing H+ from the solvent. If there is no H+ to take, the base cannot act like a base. Is your chemical a liquid when pure? $\endgroup$ – gsurfer04 Mar 11 '16 at 12:20
  • $\begingroup$ Yes it is a liquid. It is used as a high pH boiler water treatment chemical. The previous batches of this product have always had a pH value greater than 12 as a raw product. This is the first time in 11 years of making this product that this has happened. $\endgroup$ – Dylan Le Sar Mar 11 '16 at 12:26

The concept of pH tends to break down when water is not greatly in excess of the solute (e.g. if your product is a highly concentrated amine base). The apparent pH of your product, when measured using a pH meter or an indicator, may be relatively low (seemingly less basic) if the solution has a less polar environment than that of pure water--because ionization will be less favorable.

If no water is present at all, the product might still give a pH reading with a meter or indicator, but the term "pH" in this case would be irrelevant.

It always helps to talk specifics with chemistry, so I am curious as to what the ingredients of the product are.

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    $\begingroup$ If the product has no appreciable amount of water, then dunking the pH electrode in it could ruin the electrode. The electrode works by having a hydrated layer of silica on the glass bulb. $\endgroup$ – MaxW Mar 11 '16 at 16:50
  • $\begingroup$ Worst of all, the electrode would still continue to produce some readings (seemingly sensible, but in fact random). $\endgroup$ – Ivan Neretin Mar 11 '16 at 17:53
  • $\begingroup$ Unfortunately the formula is proprietary so I cannot just post it here..... If you gave me a way to contact you on a personal level then I could divulge the ingredients but not the specific recipe for the product. $\endgroup$ – Dylan Le Sar Mar 14 '16 at 11:44
  • $\begingroup$ @DylanLeSar Keep your company secrets...the principles apply broadly in any case. $\endgroup$ – iad22agp Mar 14 '16 at 11:48
  • $\begingroup$ @iad22agp thank you though for the understanding and the answer provided. I have also brought it to out technical consultant's attention and he seems to agree with you. A person never stops learning ;) $\endgroup$ – Dylan Le Sar Mar 15 '16 at 14:16

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