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can i use Dissodium phosphate in place of soduim phosphate 56.8g how much do i use?

I would imagine you can, since it's the phosphate ion that's the important part. As for quantity, the molecular weight of disodium phosphate is 71, and the molecular weight of sodium phosphate is 60, therefore, the increase in weight is (71-60)/60 ~ 0.18. To get the same molar concentration you need to add about 20% more. if you have a specific molar concentration with 56.8g, you'd need about 10 g more, or about 66.8g.