I am shining a HeNe beam into a 1:1 solution of 40% HF and 7% potassium permanganate. Potassium permenganate is very dark purple (cannot see visible light throught it). I am shining the HeNe through about 2 millimeters depth of this solution. I was wondering how much of the beam is actually getting through and hitting my sample at the bottom, or if the affects would just be neglegible. I am considering using sodium permanganate because I need a higher concentration, however, a solution of sodium permanganate will be dark red, though I don't know how dark yet because I have not ordered any. I can't dilute the potassium permanganate without lessening its effects. Even if I were to dilute it, the purple color would not decrease enough anyway. Please give me any tips you can. thank you.