Trace Metal solubility - (Apr/05/2011 )

Hi guys,

I'm trying to test solubility of Minerals in water. My 1000x trace metal recipe is:
a. 50mM FeSo4.7H2O (no problem dissolving it separately)
b. 10mM MnCl2.4H2O (no problem dissolving it separately)
c. 2mM CoCl2.6H2O (no problem dissolving it separately)
d. 10mM ZnSo4.7H2O (no problem dissolving it separately)
e. 2mM NiSO4.6H2O (no problem dissolving it separately)
f. 2mM (NH4)6Mo7O27.4H2O (no problem dissolving it separately)
g. 20mM CaCl2 (White cloudy)
h. 2mM CuCl2 (no problem dissolving it separately)
i. 2mM H3BO3 (no problem dissolving it separately)

question 1: How do I get CaCl2 to dissolve?
question 2: Trace metal solution turn dark after adding(NH4)6Mo7O27.4H2O. I think it might be oxide formation. I have some bad feelings about this color change. Some people use Na2MoO4, what do you guys use? facing similar problems?

Thank you in advance for any suggestions.
ILJ

1: with so many sulfates around you will get formation of calcium sulfate which is not as soluble as calcium chloride.

You addition of a ammoniate of molybdinum may be altering the pH of the solution (I'm guessing here, not a chemist) which could precipitate the Mn as well.

Have you tried making the solutions separately at the 1000x concentration and adding each to the 1x separately?

THANK YOU ALL for your valuable comments!

bob1, I made each solution separately, then combine them all to make 1000x stock solution. I just check the pH of 66mM (NH4)6Mo7O27.4H2O, pH is around 5.1

mdfenko, when I heat sterilized 1M CaCl separately, I can see light orange powder crashing out prior to mixing with other metals. So I tried again, this time 1M CaCl in 60 mM HCl. It's clear. And it mix perfectly with other metals.

I very curious about the color change when mixing (NH4)6Mo7O27.4H2O with other metals.
ILJ