Percipitate while pH setting of insect ringer - (Apr/29/2015 )
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!
probably magnesium hydroxide.
you should adjust the pH prior to addition of mgcl2.
I did some fast calculation in Minteq and the precipitate might be MgHPO4*3H2O and Mg(OH)2, although the calculations are not completely reliable due to the extremely high ionic strength. I guess you tried to prepare a stock rather than the working solution because ~16% of salts is a lot