Testing 88% lactic acid

I would like to test my lactic acid. If I add 1 ml of 88% lactic acid to 1 gallon of distilled water what pH can I expect to achieve? Is this a good way of testing?
We were messing around on xmas turning a brett beer into a sour. I wake up the next day and the lactic was left out all night and had a syringe sitting in it. I thought nothing of it but then missed my next mash pH by .4 points next brew day and this has never happened. Which is why I'm interested.

No.You test it by seeing how much base it will 'neutralize'. 88% lactic acid is 11.8 N to mash pH (5.4). To see if it is you add 1 mL of it to a convenient volume of DI water and then add a strong base like NaOH to it in small increments keeping track of how much you are adding as you go. It should take 11.8 mEq to reach pH 5.4. If it takes 10 mEq then the strength of your acid is not 11.8 N but only 10 N and the w/w concentration is 88*(10/11.8)%.

To do this you need a solution of NaOH of convenient strength say 1 N. To get that you would dissolve 44 grams of lye in a liter of DI water (or 4.4 in 0.1L). You would then add this 1 N solution to the water with the lactic acid while monitoring pH. Each mL of the lye solution is 1 mEq.

All this is simple enough if you remember how to do this stuff from high school chem and if you have a bit of kit but if you don't then getting the solution is tough. You could probably work something with sodium bicarbonate. Make a solution of that and see how much it takes to bring 1 mL of newly bought lactic acid to pH 4 (not 5,45.4 this time) and then see how much it takes to neutralilze the old stuff to this pH. If takes 10% more then the old stuff is 88%/1.1.

Thank you AJ. I was thinking my solution was too simple, especially with nothing to buffer in the DI water.

I have some Ca(OH)2 but of dubious purity as well. Think I'll just buy some new lactic. Thanks for always taking the time.