Having trouble mixing some salts.....

[pippo]

People,

 

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.

[Sensei]

You have remains of strong acid SO₄^2-
mixed with remains of weaker acids NO₃^- and H₂PO₄^- (or PO₄^3- 2H⁺ )
mixed with ions Ca²⁺ and Mg²⁺ which are often creating compounds barely soluble in water..

 

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

 

https://en.wikipedia.org/wiki/Calcium_sulfate

"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.

 

https://en.wikipedia.org/wiki/Precipitation_(chemistry)

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 October 24, 2016 by Sensei

[pippo]

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"?

[hypervalent_iodine]

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

[pippo]

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 October 26, 2016 by pippo