[Count of Monte Cristo]

I recently purchased a container of sodium free salt as a source of potassium (as the substitute replaces NaCl with KCl). However it has several other components, these being fumaric acid, tricalcium phosphate, and monocalcium phosphate. How would I go about extracting reasonably pure KCl with the basic chemistry tools that I have.

[billnotgatez]

Out of curiosity, do you know the concentrations of the constituents and what is you the level of purity you desire?

In introductory chemistry this sort of thing is given as a lab.
One searches through the properties of the constituents and sees if there are differences that would allow for separation. For example solubility in water. If you had table salt and sand the salt would dissolve and the sand would not dissolve. Another, property might be chemical. For instance if you had table salt and ethanol the ethanol would burn and the table salt would not typically burn.

Can you find properties that might work for you.

[Count of Monte Cristo]

As for purity it just has to be pure enough so that I could use it for other reactions with negligible interference from the impurities.

As for the concentrations:

There is a total of ≈88.6g of salt substitute, it was given that there are 610mg (0.61g) of potassium per serving. Because there were 74 servings I got a total of 88.39g of KCl, this leaves just 0.21g of the other three remaining substances (fumaric acid, mono and tri Calcium Phosphates).

I also found approximate values for the solubilities of all four substances, though none of them are very high, there is still a huge gap in KCl and the other three. KCl: 34.4g/100mL, C₄H₄O₄: 0.63g/100mL, Ca₃(PO₄)₂: 0.002g/100mL, Ca(H₂PO₄)₂: 2g/100mL

Based on this I would probably have the most success with dissolving portions of it in water and filtering out the insoluble portions. But how would I know how much water to use so that the unwanted substances are not dissolved? Also, how could fumaric acid be turned into a solid if, as far as I know, when acids aren't dissolved in water they're gasses?

[billnotgatez]

If you had enough water to dissolve
88.39 grams of   potassium chloride            KCl: 34.4   g/100mL (almost 257mL)
then you could also be dissolving approximately
 1.62 grams of   fumaric acid               C₄H₄O₄:  0.63  g/100mL
 5.14 grams of   monocalcium phosphate  Ca(H₂PO₄)₂:  2     g/100mL
 0.0051 grams of tricalcium phosphate    Ca₃(PO₄)₂:  0.002 g/100mL
and you only have
 0.21   g of these other three

You do not have the actual values for these other three and it is my guess that each one of them are at levels that could be dissolved. It is just a guess based on probable use of water in the purification of the product,

What other properties could be used to remove the other three and leave the potassium chloride?

By the way in the end you will not have exactly have just potassium
instead you will have the compound that is made of potassium and chloride.

I say this because you made this statement and I am not sure you have a total grasp of the knowledge you need.

as far as I know, when acids aren't dissolved in water they're gasses

But, we can learn.


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[billnotgatez]

To help us I am posting these links
Fumaric acid
http://www.chemspider.com/Chemical-Structure.10197150.html?rid=8af51423-6a84-4bd6-899a-ac671e799055
http://en.wikipedia.org/wiki/Fumaric_acid

Monocalcium phosphate or Calcium dihydrogen phosphate
http://www.chemspider.com/Chemical-Structure.22862.html
http://en.wikipedia.org/wiki/Monocalcium_phosphate

Tricalcium phosphate
http://www.chemspider.com/Chemical-Structure.22864.html?rid=7419ff0f-ff62-47da-bb1d-424db8fceb8f
http://en.wikipedia.org/wiki/Tricalcium_phosphate

potassium chloride
http://www.chemspider.com/Chemical-Structure.4707.html?rid=3008eb0f-4887-4018-8006-87aa0fa1669a
http://en.wikipedia.org/wiki/Potassium_chloride

[Borek]

a total of 88.39g of KCl, this leaves just 0.21g of the other three remaining substances

Depending on what you are going to do chances are KCl is already pure enough.

as far as I know, when acids aren't dissolved in water they're gasses?

That's incorrect. Some acids can be produced by dissolving gases in water, but it is by no means universal, quite the opposite - most acids are liquid or solid when pure.

[Dan]

88.39g of KCl, this leaves just 0.21g of the other three remaining substances

I've not checked your working, but that comes out as 99.8% purity - higher than most lab suppliers claim. It should be fine.