[k_amy21]

Hi,

I have a major problem with stabilizing the pH to value 7 in my solution that contains these chemicals:
Na2SiO3, CaCl2, KCl, Na2SO4, NaHCO3 and NaCl. The initial pH (after adding all of these stuff) is around 10.
The problem occurs when I start adding HCl (probably due to the present silica). I cannot for some reason stabilize the pH. It is constantly rising!!!!
I suppose I could use some buffer solution in order to adjust the pH, but the thing is I cannot add any other cations or anions other then these.
Can someone help and tell me what to do? Is there an acidic buffer solution that contains some of these cations/anions?
I would appreciate very much any suggestions, thoughts, anything that could help with solving this problem...

[Rucasta]

Do you need to have all those chemicals present?  I don't see how having so many spectator ions in your solution will make a difference to the observed pH, before and after addition of your acid.

If you are trying to make a buffer solution able to maintain a pH of 7, you may have a look in your book or online to see what pH ranges certain acid/base pairs will maintain.