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Chemistry Forums for Students => Analytical Chemistry Forum => Topic started by: Carlaz on February 08, 2010, 11:51:28 AM

Title: Problem with dissolving a number of salts
Post by: Carlaz on February 08, 2010, 11:51:28 AM

Hi, I'm having some problems dissolving a number of salts into water. The salts are:

KI- ~4g
CaCl2~20g
MgSO4 ~ 1g
CaHCO3 ~2g

The solution is being made up with phosphate buffer and then being topped off to 1 L. The solution pH is 6.2 but the salts wont dissolved. I have tried heating and sonicating them. Does anyone know of a way to dissolve salts that don't want to go into solution? The exact quantities of ions need to remain relatively constant as i wish to measure the toxicity of each ion.

Title: Re: Problem with dissolving a number of salts
Post by: Borek on February 08, 2010, 12:33:55 PM

Calcium phosphate?

Title: Re: Problem with dissolving a number of salts
Post by: Carlaz on February 08, 2010, 12:50:44 PM

No its the K and Na phosphate buffer

Title: Re: Problem with dissolving a number of salts
Post by: Borek on February 08, 2010, 02:26:19 PM

Obviously you didn't get my hint. I have not checked K_sp values so I can be wrong, but HS solubility rules tell me to look for solid calcium phosphate in your solution. Have you ruled out this possibility?

Title: Re: Problem with dissolving a number of salts
Post by: Carlaz on February 08, 2010, 03:04:44 PM

Now that would make sense of my observation of there being more solids in the solution than what i put in there at the start. Now i need to think how i can remove the PO₄ effect.

Title: Re: Problem with dissolving a number of salts
Post by: OrthoParaDirector on February 09, 2010, 01:40:45 PM

http://en.wikipedia.org/wiki/Solubility_table

Here you can check if combinations of salt are soluble.