Discussion – Spirits, Essential Oils, Vinegar

OK, I understand.
1) Measuring the pH value: as already said, from one integer figure to the next one it's tenfold more diluted or more concentrated. Therefore dilute your sample in a ratio of 1 + 9. If the pH is below 7, add 1 to the estimated read off, if the pH is higher than 7 substract 1 from the estimated read off.
2) The proposed dosage of the liquid acid blend is 300 to 400 ml per 100 liters of fruit mash (brand name "Biogen M", manufacturer "Oestreich GmbH"), no matter the start pH. You could make a saturated solution with your solid acid blend and add this solution instead. Hence dissolve as much as possible in lukewarm water, will say pour and stir until the new added solid parts are not dissolving anymore.
No, unfortunately I don't know any supplier of liquid acid blends in North America.

I wish mush success!