3 replies to this topic

[ILoveJuice]

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)[color clear]
b. 10mM MnCl2.4H2O (no problem dissolving it separately)[color light pink]
c. 2mM CoCl2.6H2O (no problem dissolving it separately)[color pink]
d. 10mM ZnSo4.7H2O (no problem dissolving it separately)[color clear]
e. 2mM NiSO4.6H2O (no problem dissolving it separately)[color light green]
f. 2mM (NH4)6Mo7O27.4H2O (no problem dissolving it separately)[color clear]
g. 20mM CaCl2 (White cloudy)
h. 2mM CuCl2 (no problem dissolving it separately)[color light blue]
i. 2mM H3BO3 (no problem dissolving it separately)[color clear]

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

[mdfenko]

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

[bob1]

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?

[ILoveJuice]

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