[guguma]

Hi All,

I am trying to make a 0.1M CaBr₂ solution in water, CaBr₂ I have is from Alfa-Aesar %99.5 (Anhydrous). CaBr₂ should be highly soluble ≈ 125g/100ml, my solution is ≈ 20g/L, yet it does not dissolve. What I see is more like a suspension of whitish particulates no matter how much I stir/heat the solution. I am assuming that it should be clear.

Water I am using is DI Millipore Grade, I am completely baffled, any insights would be greatly appreciated.

Thank You

[Archer]

How confident are you on the age, quality and identity of your materials?

[guguma]

It just arrived from Alfa-Aesar, so I am confident about the age. Quality and Identity, I am not certain at this point, I am a physicist who found himself in a biology lab and unfortunately I am quite ignorant about these materials. However, I did receive contaminated products from companies before, and while I was washing out the funnels I used for this salt (one glass, one plastic) a whitish residue just insists on staying on the funnel, it does not matter how much water I use to rinse it with and it raises a HUGE red flag about this substance.

I ordered this through Fisher Scientific since this had a higher purity than what was available at Sigma Aldrich, anything I get from Fisher is, how should one put it, mediocre at best. But I do want to be certain before I call them to send this back.

Would you offer me some quantitative tests (procedures) to determine the quality and/or identity of the substance?

Thank You.

[curiouscat]

Hi All,

I am trying to make a 0.1M CaBr₂ solution in water, CaBr₂ I have is from Alfa-Aesar %99.5 (Anhydrous). CaBr₂ should be highly soluble ≈ 125g/100ml, my solution is ≈ 20g/L, yet it does not dissolve. What I see is more like a suspension of whitish particulates no matter how much I stir/heat the solution. I am assuming that it should be clear.

Perhaps what you see as suspension is the left over 0.5%?

Have you filtered & weighed the insolubles?

[Archer]

You could also see if lowering the pH with HCl clarifies the solution. There may be some other calcium salts present.

If it is still a suspension then you may have some other material contaminant.

[Babcock_Hall]

Just a WAG but some calcium salts are quite insoluble, and you may be looking at one or more of those.  I might be tempted to filter the suspension and dry the particulate matter.  One could do a titration for calcium.

[Babcock_Hall]

Calcium carbonate is not very soluble, and your water may have carbon dioxide from the atmosphere.  Possibly you can degas the water in some way.

[guguma]

I filtered the solution with a vacuum filtration system, the result is a clear liquid, its density is close to what one would expect, I am dessicating the remnants to weight the remnants too, however this test is not quantitative enough considering the accuracy I require, I might need to do some titration to get an idea about the actual concentration of CaBr₂ that remains in the filtered solution.

 

[curiouscat]

I filtered the solution with a vacuum filtration system, the result is a clear liquid, its density is close to what one would expect, I am dessicating the remnants to weight the remnants too, however this test is not quantitative enough considering the accuracy I require, I might need to do some titration to get an idea about the actual concentration of CaBr₂ that remains in the filtered solution.

My impression is what you were seeing as suspension was impurities or some by-products. A bulk of your CaBr2 is already in solution, I think.

[Babcock_Hall]

Calcium ions could be titrated with EDTA.  For example:
http://faculty.ccri.edu/aahughes/GenChemII/Lab%20Experiments/Calcium_Analysis_EDTA_Titration.pdf

Inorganic chemistry is not my field, so others here may have better suggestions.