Experimental tests
A number of experiments have been carried out to test
the accuracy and resolution of the instrument applied to:
The sizes of calibration latexes with mean radii 0.05, 0.1,
0.135, and 0.25 microns dissolved in water and with the width of
the polydispersity distribution less than 6% have been
measured. The latexes were produced and calibrated by the
Lebedev Rubber Research Institute, St. Petersburg, Russia.
With the assumption that the polydispersity distribution is
symmetrical, the inaccuracy of the mean radius determination
does not exceed 1.5 % in each case.
The particle-size measurements in an opaque system (black
aniline dye dissolved in water) have also been performed. The
dye concentration was changed from that corresponding to
absolutely transparent to opaque solutions. In the latter case
the light penetration into the sample did not exceed 0.5 mm.
As is seen from the figure below, for all dye concentrations,
the measured radius is stable within 5%.
![[Picture]](dye.gif)
The measurements were
carried out with ”backscattering” 1350 geometry (solid squares in the above figure).
The conventional 900 geometry in a cylindrical
cell has also been used for the smallest concentration (0.01%) at which the solution is transparent(a circle in the figure).
The diffusion coefficient and particle size of
polystyrene of molecular weight Mw = 96,400
dissolved in toluene, at 22 0C has been measured.
The mass concentration of polystyrene
was 0.0217 g cm-3. Two optical geometries and sample
cells were used: with scattering angles of 450 (a round
glass cell of the diameter 27.25 mm) and 900 (a square cell of 12.5 x 12.5 mm). The scattering in this system is very weak. Such conditions are not favorable for accurate measurements.
Nevertheless, excellent agreement
with precision other-technique measurements of the diffusion coefficient in this system has been obtained. See Refs. [19,20] in the Related literature section.
Back to the
Photon-Correlation Spectrometer page