What is the molar absorptivity of copper sulfate? I am trying to find the molarity of copper sulfate solution by absorption in a spectrophotometer with a cuvette.
However, I can't find \varepsilon, the molar absorptivity coefficient of \ce{CuSO4}. I searched it up online, and I found experimental data saying that is \pu{2.81 L mol-1 cm-1}, but another source says that it is 0.91.
I have searched on various databases including NIST's, but I couldn't find anything. Is there a definite molar absorptivity for everything, or is it all experimental?