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Having trouble mixing some salts.....

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#1 pippo



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Posted 24 October 2016 - 01:28 PM



Mixing in DI water Calcium nitrate tetrahydrate, K Phos Monobasic, and Mg Sulfate, about 2% each. I am not sure if it is the sulfates or the phosphate that causes solution to get cloudy with ppt. Tried also to lower pH from initial 3.8 to 3 or so with dil sulfuric. Any one know what is causing the cloudiness?


I still have to add KNO3 and K2SO4 in even smaller qtys but I stopped here as no need to proceed with a bad/turbid solution


Tips appreciated.

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#2 Sensei



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Posted 24 October 2016 - 03:32 PM

You have remains of strong acid SO42-
mixed with remains of weaker acids NO3- and H2PO4- (or PO43- 2H+ )
mixed with ions Ca2+ and Mg2+ which are often creating compounds barely soluble in water..


CaSO4 is barely soluble in water. and has milky look.


"Solubility in water
0.21g/100ml at 20 °C (anhydrous)[1]
0.24 g/100ml at 20 °C (dihydrate)[2]"


Put solution on shelf for couple hours and see whether there is gathering precipitate on the bottom of flask after a while.



If you mix f.e. silver nitrate salt solution with potassium chloride salt solution,

there is precipitating solid AgCl on the bottom, while potassium nitrate will remain dissolved.

Because silver chloride is barely soluble in water.


Probably you have similar reaction.

Edited by Sensei, 24 October 2016 - 04:25 PM.

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#3 pippo



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Posted 24 October 2016 - 05:13 PM

Thanks, sensei. Note that the solution is bad even before I added the weak sulfuric acid. So whatever problems there are were there to begin with. I just tried the H2SO4 for the sake of it realizing I have nothing to lose. So, how are some manufacturers doing this? What's the chemistry "secret"?

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#4 hypervalent_iodine


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Posted 24 October 2016 - 11:00 PM

You've quite possibly made caclium or magnesium phosphate, or calcium sulphate (most likely) by mixing those three salts together. None are very soluble.
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#5 pippo



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Posted 26 October 2016 - 01:17 PM

Thanks. I need to mess around with this more and see if theres a way around it........Who knows, maybe sequence of addition may matter.

Edited by pippo, 26 October 2016 - 01:18 PM.

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