March 28, 2024, 10:36:55 PM
Forum Rules: Read This Before Posting


Topic: Poor yield on CaSO4*2H2O  (Read 15173 times)

0 Members and 1 Guest are viewing this topic.

Offline Borek

  • Mr. pH
  • Administrator
  • Deity Member
  • *
  • Posts: 27633
  • Mole Snacks: +1799/-410
  • Gender: Male
  • I am known to be occasionally wrong.
    • Chembuddy
Re: Poor yield on CaSO4*2H2O
« Reply #15 on: September 09, 2009, 12:00:52 PM »
I haven't checked it. I relied on Certificate of Analysis of 99.5% pure CaCO3 that I dissolved in Nitric Acid.

Sounds reasonable.

Could be your water content is not what you expect it to be, I am afraid I can't be of help any further.
ChemBuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation, titrations.info

Offline BluRay

  • Full Member
  • ****
  • Posts: 154
  • Mole Snacks: +9/-2
Re: Poor yield on CaSO4*2H2O
« Reply #16 on: September 09, 2009, 03:18:46 PM »
I haven't checked it. I relied on Certificate of Analysis of 99.5% pure CaCO3 that I dissolved in Nitric Acid.
Did you boil the solution after having dissolved CaCO3 with HNO3? Otherwise you can have HCO3- ions which could keep Ca++ ions in solution (if I remember well). Boiling the solution eliminates dissolved CO2 and so H2CO3 and HCO3- ions.

Offline covek11

  • Regular Member
  • ***
  • Posts: 21
  • Mole Snacks: +0/-0
Re: Poor yield on CaSO4*2H2O
« Reply #17 on: September 10, 2009, 10:00:17 AM »
No, I didn't boil it.

Offline Borek

  • Mr. pH
  • Administrator
  • Deity Member
  • *
  • Posts: 27633
  • Mole Snacks: +1799/-410
  • Gender: Male
  • I am known to be occasionally wrong.
    • Chembuddy
Re: Poor yield on CaSO4*2H2O
« Reply #18 on: September 10, 2009, 11:02:30 AM »
Otherwise you can have HCO3- ions which could keep Ca++ ions in solution (if I remember well). Boiling the solution eliminates dissolved CO2 and so H2CO3 and HCO3- ions.

In the presence of excess sulfuric acid HCO3- won't survive long enough in the solution.

Besides, I think you may be mixing two things - HCO3- doesn't 'keep' Ca2+ in solution, but Ca(HCO3)2 is much better soluble in water. Thus water kept over solid CaCO3 will have higher concentration of Ca2+ when saturated with CO2.
ChemBuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation, titrations.info

Offline BluRay

  • Full Member
  • ****
  • Posts: 154
  • Mole Snacks: +9/-2
Re: Poor yield on CaSO4*2H2O
« Reply #19 on: September 10, 2009, 03:19:10 PM »

In the presence of excess sulfuric acid HCO3- won't survive long enough in the solution.
Yes, but he said to have adjusted the pH to 7.

Quote
Besides, I think you may be mixing two things - HCO3- doesn't 'keep' Ca2+ in solution, but Ca(HCO3)2 is much better soluble in water. Thus water kept over solid CaCO3 will have higher concentration of Ca2+ when saturated with CO2.
You're right.

Sponsored Links