[baseball07]

Hello.  I received a recipe from a friend and he claims it is .1M PBS.  I have never worked with buffer before, how do you determine the molarity, from the Phosphate or NaCl?  This is my recipe:

For 4L

NaH2PO4 = 7.32g
Na2HPO4 = 48.024g
NaCl = 36.008
Sodium Azide = .4g

Thank you!!

[Dan]

how do you determine the molarity, from the Phosphate or NaCl?  This is my recipe:

For 4L

NaH2PO4 = 7.32g
Na2HPO4 = 48.024g
NaCl = 36.008
Sodium Azide = .4g

The molarity given seems to be based on the monosodium phosphate

48 g / 120 g mol^-1 = 0.4 mol
0.4 mol / 4 dm³ = 0.1 mol dm^-3 (= 0.1 M)