Dryl’s buffer

Recipe

Reagent	Quantity (for 4 L)	Final concentration
H₂O	~3.6 L
Sodium citrate (0.1 M)	80 mL	2 mM
NaH₂PO₄ (0.1 M)	40 mL	1 mM
Na₂HPO₄ (0.1 M)	40 mL	1 mM
CaCl₂ (0.1 M)	60 mL	1.5 mM
H₂O	to 4 L

Add reagents in the order listed. Add CaCl₂ last (just prior to the second addition of H₂O which brings the volume to 4 L) to avoid precipitation of calcium phosphate.
The solution was developed by Dryl (Dryl SJ. 1959. Antigenic transformation in Paramecium aurelia after treatment during autogamy and conjugation. J Protozool 6: S25).