jlbarkley

I work in industry water chemistry. I am trying to figure out how effectively build a chart that would indicate the pH of water with phenol red using the absorbance value at 560nm wavelength. I know the concentration of phenol red matters and it will change the absorbance of the pH. So let's assume I am using 5ml of phenol red and 45ml of water. I can figure out concentration later. How would I even test the method? How would I find an exact pH of 7, 7.1, 7.2, 7.3..... etc. to even be able to figure out the absorbance? I essentially want a chart that when I test 10 ml of water and test it on a Hach DR900 under the 560 wavelength I can read the meter output (absorbance), look at the chart, and know the exact pH. There has to be some sort of calculation I can do for this. I have searched everywhere. I see graphs and curves for this exact thing, but it's all visual. I can never find the exact data they're using so I can calculate it myself.