I'm trying to make a stock solution for my buffers and was wondering if it's even possible to make a 1M disbasic sodium phosphate solution? I've been shaking this bad boy for so long and it doesn't seem like all of the reagent wants to get into solution! I have a heptahydrate chemical, weighed out 13.4g for a total ovlume of 50mL. The MW is 268.07g/mol. Unless I had a brain fart and did the wrong calculations.....
You must be saturating the water with the salt. Anyway, I do not recommend preparing such high concentration of phosphate as precipitation will occur if temperature slightly drops overnight.
You can purchase 1 M dibasic sodium phosphate solution, so it is possible to make it, and it is stable in solution at room temperature. It doesn't crystallize out, showing that it is not supersaturated.
Even knowing that, I have personally experienced difficulty in preparing this solution. I have even seen that it could be prepared in one place and not another. I would love to know why.
In any case, give yourself a break and make a 0.5 M solution.
But in this case how can we prepare Sodium -phosphate buffer at 0.1M ?
The molecular weight of anhydrous Na2HPO4 is 141.96 g/mol. I could prepare 0.5 M Na2HPO4 by stirring for a long time. It seemed supersaturated. I recommend the concentrations below 0.5 M.
In case anyone else comes back to this question like I did -- I really needed a 2M solution of sodium phosphate to make a 10X buffer and thought I'd just try it. Although it's true that it's supersaturated and precipitates at the slightest agitation at RT, it will go into solution at 37 degrees Celsius. It doesn't take terribly long, and if you're using it only occasionally like I am to make other solutions, it's manageable to warm it up each time.
I could prepare 0.5M Na2HPO4. 7H2O by some heating without any problem.
How to prepare the saturated Na2HPO4, facing the issue with recrystalization.
This solution mentioned in Ethanol monograph for IPA and Acetone limit test.
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