I've been trying to find the dissociation constant of borax and sodium metaborate, unsuccessfuly.
I think that if a conjugate K is known, then we can know the K (by just replacing ka by kb or viceversa), but I don't know the conjugates neither.
Maybe I can dissolve some different quantities in pure water, then use kb=[B+][OH-]/[BOH]
For example, for an unkown pkB 3.67, if I measured:
Then I could see the expected logarithmic relation to concentration, and estimate kb.
I was looking for a published data, as my pH meter is not high quality, and I'm not very experienced.
It seems strange to me though, as borax is such a common chemical, very much used.