October 31, 2024, 07:56:45 PM
Forum Rules: Read This Before Posting


Topic: Job's Method  (Read 8057 times)

0 Members and 1 Guest are viewing this topic.

Offline horsebox

  • Regular Member
  • ***
  • Posts: 45
  • Mole Snacks: +3/-1
Job's Method
« on: January 25, 2010, 05:47:43 PM »
I'm having trouble finding info on Jobs method of continuous variation because entering the word job into google yields results about jobs crazily enough.

So what I think I know about Jobs method is that it is a method of determining the stoichiometry of a reaction by preparing a series of solutions with varying concentrations of each reactant but the combined number of moles of reactants being equal among every solution. What I don't understand is the spectrophotometry part. Using the binding of Cu2+ ions to EDTA ligands as an example from what I read the concentration of the product (Cu/EDTA complex) is then determined using a spectrophotometer. I can see that the maximum amount of product will be formed in the solution whos mole fraction is closest to the actual stoichiometric ratio but wouldn't the unreacted Cu2+ and EDTA in all the other solutions influence the absorbance recorded by the spectrophotometer?

Offline Borek

  • Mr. pH
  • Administrator
  • Deity Member
  • *
  • Posts: 27820
  • Mole Snacks: +1808/-412
  • Gender: Male
  • I am known to be occasionally wrong.
    • Chembuddy
Re: Job's Method
« Reply #1 on: January 26, 2010, 02:14:12 AM »
http://lmgtfy.com/?q=Jobs+method+of+continuous+variation

1. You can try to select wavelength at which only complex absorbs.

2. Even if that's impossible it only means that math is a little bit more complicated.
ChemBuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation, titrations.info

Offline JGK

  • Chemist
  • Full Member
  • *
  • Posts: 738
  • Mole Snacks: +66/-19
  • Gender: Male
Re: Job's Method
« Reply #2 on: January 27, 2010, 02:15:56 PM »
You will have much success if you google Job's method of continuous variation
Experience is something you don't get until just after you need it.

Sponsored Links