20x concentrated sodium chloride/sodium citrate stock solution.
3 M NaCl, 300 mM sodium citrate, pH = 7.0, microfiltered, steam sterilised.

By diluting the stock solution you get a versatile blotting, hybridization and washing buffers for Southern and Dot/Slot-Blots of DNA as well as for in situ hybridizations. Undiluted buffer is also suitable for neutral transfer of RNA onto unloaded membranes.