I have a big problem: I´m preparing an insect ringer solution (pH 7,4; total volume 100 ml) with those ingredients
2.35ml 2M KCl
3.7ml 2M KH2PO4
All ingredients dissolve excellently. The starting value of pH is app. 4,4. When I was trying to set up 7,4 by NaOH or KOH everything was working fine. But at the point of 7,0 - 7,1 there was percipitation.
Has anybody an idea what could be the reason for that percipitation or what substance I could use to set up the pH instead of NaOH/KOH?
Thanks in advance!