Chemical Forums
Specialty Chemistry Forums => Biochemistry and Chemical Biology Forum => Topic started by: guguma on October 08, 2013, 10:19:55 PM
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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
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How confident are you on the age, quality and identity of your materials?
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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.
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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?
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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.
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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.
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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.
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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.
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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.
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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.