March 28, 2024, 04:33:56 AM
Forum Rules: Read This Before Posting


Topic: Dispute on the accuracy of this serial dilution  (Read 1637 times)

0 Members and 1 Guest are viewing this topic.

Offline Tyyyyuuu

  • New Member
  • **
  • Posts: 5
  • Mole Snacks: +0/-0
Dispute on the accuracy of this serial dilution
« on: September 28, 2020, 01:33:36 PM »
I think the last dilution in this series is 1 in 5 not, as it indicates in the table, 1 in 10. Am I wrong?!?! (the unit of volume is arbitrary, but lets say mL)

Offline Borek

  • Mr. pH
  • Administrator
  • Deity Member
  • *
  • Posts: 27637
  • Mole Snacks: +1799/-410
  • Gender: Male
  • I am known to be occasionally wrong.
    • Chembuddy
Re: Dispute on the accuracy of this serial dilution
« Reply #1 on: September 28, 2020, 04:32:58 PM »
That would mean all earlier dilutions are wrong as well, wouldn't it?
ChemBuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation, titrations.info

Offline Tyyyyuuu

  • New Member
  • **
  • Posts: 5
  • Mole Snacks: +0/-0
Re: Dispute on the accuracy of this serial dilution
« Reply #2 on: September 28, 2020, 05:17:25 PM »
That would mean all earlier dilutions are wrong as well, wouldn't it?

Thank you for your input. I suppose the "analytical dilution" makes sense if it's intended to be relative to just the prior dilution, and not the original stock solution. But if that's the case then the last dilution is 1 in 5 relative to the penultimate dilution.  ???
« Last Edit: September 28, 2020, 05:29:04 PM by Tyyyyuuu »

Offline Borek

  • Mr. pH
  • Administrator
  • Deity Member
  • *
  • Posts: 27637
  • Mole Snacks: +1799/-410
  • Gender: Male
  • I am known to be occasionally wrong.
    • Chembuddy
Re: Dispute on the accuracy of this serial dilution
« Reply #3 on: September 28, 2020, 05:42:02 PM »
No, I think you are misunderstanding something here. These dilutions are cumulative, each next one uses the previous solution.

But if that's the case then the last dilution is 1 in 5 relative to the penultimate dilution.

No, it is 1.25 (240/192).
ChemBuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation, titrations.info

Offline Tyyyyuuu

  • New Member
  • **
  • Posts: 5
  • Mole Snacks: +0/-0
Re: Dispute on the accuracy of this serial dilution
« Reply #4 on: September 28, 2020, 06:28:09 PM »
No, I think you are misunderstanding something here. These dilutions are cumulative, each next one uses the previous solution.

But if that's the case then the last dilution is 1 in 5 relative to the penultimate dilution.

No, it is 1.25 (240/192).

I follow what you are saying, but this is my line of thinking:

From the first row in the table, to the last:

450 mL diluent + 450 mL analyte is a 1 in 2 dilution
320                 + 640                        1 in 3
240                 + 720                        1 in 4
180                 + 720                        1 in 5
130                 + 650                        1 in 6
090                 + 540                        1 in 7
055                 + 385                        1 in 8

048                 + 640                        1 in 5 (not 1 in 10)

Offline Borek

  • Mr. pH
  • Administrator
  • Deity Member
  • *
  • Posts: 27637
  • Mole Snacks: +1799/-410
  • Gender: Male
  • I am known to be occasionally wrong.
    • Chembuddy
Re: Dispute on the accuracy of this serial dilution
« Reply #5 on: September 28, 2020, 06:53:42 PM »
048                 + 640                        1 in 5 (not 1 in 10)

Why 640 and not 192? You have changed the rules for this one line.
ChemBuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation, titrations.info

Offline Tyyyyuuu

  • New Member
  • **
  • Posts: 5
  • Mole Snacks: +0/-0
Re: Dispute on the accuracy of this serial dilution
« Reply #6 on: September 28, 2020, 07:04:08 PM »
048                 + 640                        1 in 5 (not 1 in 10)

Why 640 and not 192? You have changed the rules for this one line.

You're right, sorry, that was an error, (but the conclusion is the same)

450 mL diluent + 450 mL analyte is a 1 in 2 dilution
320                 + 640                        1 in 3
240                 + 720                        1 in 4
180                 + 720                        1 in 5
130                 + 650                        1 in 6
090                 + 540                        1 in 7
055                 + 385                        1 in 8

048                 + 192                        1 in 5 (not 1 in 10)

Offline Borek

  • Mr. pH
  • Administrator
  • Deity Member
  • *
  • Posts: 27637
  • Mole Snacks: +1799/-410
  • Gender: Male
  • I am known to be occasionally wrong.
    • Chembuddy
Re: Dispute on the accuracy of this serial dilution
« Reply #7 on: September 29, 2020, 02:59:37 AM »
Your results are inconsistent. Show how you got 1 in 5 in the last line and explain how you got correct results for all previous lines.
ChemBuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation, titrations.info

Offline Tyyyyuuu

  • New Member
  • **
  • Posts: 5
  • Mole Snacks: +0/-0
Re: Dispute on the accuracy of this serial dilution
« Reply #8 on: September 29, 2020, 03:07:04 AM »
Your results are inconsistent. Show how you got 1 in 5 in the last line and explain how you got correct results for all previous lines.

Is 1 mL A plus 1 mL of water not a 1 in 2 dilution of A? That is, one unit of A in a total of 2 units of solution.

Offline Borek

  • Mr. pH
  • Administrator
  • Deity Member
  • *
  • Posts: 27637
  • Mole Snacks: +1799/-410
  • Gender: Male
  • I am known to be occasionally wrong.
    • Chembuddy
Re: Dispute on the accuracy of this serial dilution
« Reply #9 on: September 29, 2020, 03:12:30 AM »
It is, but what about the next one?

Perhaps you are missing the fact that each next step uses not the original stock solution, but solution from the previous step? That's what 'serial' means.
ChemBuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation, titrations.info

Sponsored Links