Zimm Plot Gathered on Phoenix Instrument
Convert your scattering data obtained on polystyrene sulfonate into a Zimm plot, following the
general method in the “HowTo” guide. You can do it in Excel, although the HowTo is wrapped
around a program called GuiDe (also known as NonZimm). You can use the dn/dc value you
obtained earlier. You may have to make an assumption or two to get your concentrations in the
required units (g/cm3).
Other stuff you need: we used an Argon-Krypton mixed gas laser operating at o = 514.5 nm.
The optics were set so that m=1 in the equation regarding how volume should compare from
Rayleigh standard (toluene) to the solutions (also toluene). The refractive index of toluene is
about 1.495 and that of your solutions about 1.33. Other things can be found on the website
(http://macro.lsu.edu/HowTo/guide/guide.doc ) especially the appendix and, within that, the
section entitled Mechanics of Gathering Data. Once you have Excel make the plot, you may very
well find it easiest to just draw the rest graphically.
a) Specify what concentrations you prepared (by weight).
b) Specify your concentrations as g/mL and list any approximations required to make the
conversion.
c) Specify how you got your dn/dc value (in most cases, using the CN Wood differential
refractometer).
d) Specify the value you obtained, being sure to include a ± uncertainty term.
e) Specify what angles you measured.
f) Show the I·sin() / I(=90°) vs.  plot for solvent.
g) Show your Zimm plot as just bare points.
h) Draw the c = 0 and  = 0 extrapolation lines.
i) Determine Mw, A2 and Rg, if possible. Each one needs a ± estimate.
Grading Rubric: 50 points total
27 points: 3 points for each of the items above)
10 points: evidence for critical thought and reflection about what went wrong or right during
measurements, integrated with the information above).
13 points: quality of the results (full credit for publication-quality work)