Eastern Regional Research Laboratory, Philadelphia, Pennsylvania
†Present address: Ohio State University, Columbus, Ohio.
‡One of the laboratories of the Bureau of Agricultural and Industrial Chemistry, Agricultural Research Administration, United States Department of Agriculture.
B. A. Brice, M. Halwer, and R. Speiser, "Photoelectric Light-Scattering Photometer for Determining High Molecular Weights*," J. Opt. Soc. Am. 40, 768-778 (1950)
A photoelectric photometer designed for the measurement of absolute turbidity, dissymmetry, and depolarization of dilute solutions of high molecular weight materials, and hence determination of their molecular weights, is described. The photometer comprises essentially a monochromatic parallel primary beam of radiation, a six-sided scattering cell for measurements at 0°, 45°, 90°, and 135°, a multiplier phototube and galvanometer, a standard opal glass diffusor, and removable polarizer and analyzer. Turbidity is determined in terms of a ratio of deflections for the 90° scattering and for the primary beam reduced in intensity by neutral filters and diffused by an opal glass plate. Working relationships leading to determination of absolute turbidity are developed. These relationships include corrections for refraction and reflection effects, and for imperfect diffusion by the opal glass. The latter is evaluated by comparison of the opal glass with reflecting diffusors corrected for specular component of reflectance. The response of some multiplier photo-tubes is shown to be dependent on the plane of polarization of the incident radiation. Data illustrating the performance of the photometer include comparison of molecular weights of polystyrene fractions, beta-lactoglobulin, bovine serum albumin, lysozyme, sucrose octaacetate, Raleigh’s ratio and depolarization for benzene, turbidity of a “standard” polystyrene, and particle size of a GR-S latex, with data obtained by other methods or other investigators.
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White structural glass ground with No. 320 carborundum.
Block scraped with straightedge.
0.5-mm layer smoked onto MgCO3 from burning Mg chips.
Commercial casein paints of different brands; painted on Vitrolite.
Pressed layer of the dry powder, about 1 mm thick on Vitrolite.
Absolute reflectance [see F. Benford, G. P. Lloyd, and S. Schwarz, J. Opt. Soc. Am. 38, 445 (1948)]. All other values of R determined on G. E. spectrophotometer relative to MgO and corrected to absolute reflectance.
Ratio of deflections for horizontal and vertical getting of analyzer; incident radiation unpolarized.
Proportion of reflected radiation polarized [see R. W. Wood, Physical Optics, third edition (Macmillan, New York, 1934), p. 341].
Analyzer not present when measuring GR/G0.
Corrected by assuming (1−H/V)/(1+H/V) is equal to the ratio of specular to diffuse component.
Analyzer present (horizontal setting) when determining GR/G0.
In this case, the galvanometer deflections for the two types of opal glass are in exact proportion to their observed diffuse transmittances.
Table III
Transmittances of neutral filters (F, photometer; T, spectrophotometer).
With working standard in place (total reduction factor about 2×10−4) and opal glass at photo-tube.
Each value of F is a mean calculated from five or six ratios of deflections; the average deviation from the mean is shown for 547 mμ.
Table IV
Dependence of multiplier photo-tube response on plane of polarization. Effectiveness of opal glass as depolarizer.
Ratio of deflections with analyzer set to pass horizontal and vertical electric vector vibrations, respectively, for unpolarized incident radiation, with standard opal glass at table center.
Table V
Dissymmetry coefficients, q, depolarization, ρu, turbidity correction factors, and refractive index increments.
Molecular weights.
By osmotic pressure.
By x-ray diffraction, F. R. Senti and R. C. Warner, J. Am. Chem. Soc. 70, 3318 (1948).
By x-ray diffraction, K. J. Palmer, M. Ballantyne, and J. A. Galvin, J. Am. Chem. Soc. 70, 906 (1948).
By osmotic pressure, G. Scatchard, A. C. Batchelder. and A. Brown, J. Am. Chem. Soc. 68, 2320 (1046).
Sum of atomic weights.
Dow Styron, kindly supplied in solid form by A. M. Bueche, Cornell University; value quoted is turbidity of 0.5 percent solution in toluene, determined for 436 mμ on the absolute camera (references 2, 4, 5) by J. R. McCartney. A more recent determination on the same camera by E. W. Anacker gave 0.00274.
From 90° scattering, 436 mμ, in apparatus similar to ours; P. M. Doty (private communication).
By transmission at 436 mμ, P. M. Doty (private communication).
Average of two independent methods involving 90° scattering at 436 mμ; 0.00340 and 0.00357; B. H. Zimm (private communication). Other data in reference 6 indicate close agreement between turbidities determined from 90° scattering and from transmission measurements in Zimm’s laboratory.
From 90° scattering, 436 mμ, F. W. Billmeyer, Jr. (private communication).
P. Peyrot, 24°C and 436 mμ, Ann. d. Physik 9, 335 (1938).
Reference 6.
By electron microscope, number average.
Tables (6)
Table I
Calibration data for turbidity equation.
Quantity
Symbol
436 mμ
546 mμ
Apparent diffuse transmittance of opal glass standard
White structural glass ground with No. 320 carborundum.
Block scraped with straightedge.
0.5-mm layer smoked onto MgCO3 from burning Mg chips.
Commercial casein paints of different brands; painted on Vitrolite.
Pressed layer of the dry powder, about 1 mm thick on Vitrolite.
Absolute reflectance [see F. Benford, G. P. Lloyd, and S. Schwarz, J. Opt. Soc. Am. 38, 445 (1948)]. All other values of R determined on G. E. spectrophotometer relative to MgO and corrected to absolute reflectance.
Ratio of deflections for horizontal and vertical getting of analyzer; incident radiation unpolarized.
Proportion of reflected radiation polarized [see R. W. Wood, Physical Optics, third edition (Macmillan, New York, 1934), p. 341].
Analyzer not present when measuring GR/G0.
Corrected by assuming (1−H/V)/(1+H/V) is equal to the ratio of specular to diffuse component.
Analyzer present (horizontal setting) when determining GR/G0.
In this case, the galvanometer deflections for the two types of opal glass are in exact proportion to their observed diffuse transmittances.
Table III
Transmittances of neutral filters (F, photometer; T, spectrophotometer).
With working standard in place (total reduction factor about 2×10−4) and opal glass at photo-tube.
Each value of F is a mean calculated from five or six ratios of deflections; the average deviation from the mean is shown for 547 mμ.
Table IV
Dependence of multiplier photo-tube response on plane of polarization. Effectiveness of opal glass as depolarizer.
Ratio of deflections with analyzer set to pass horizontal and vertical electric vector vibrations, respectively, for unpolarized incident radiation, with standard opal glass at table center.
Table V
Dissymmetry coefficients, q, depolarization, ρu, turbidity correction factors, and refractive index increments.
Molecular weights.
By osmotic pressure.
By x-ray diffraction, F. R. Senti and R. C. Warner, J. Am. Chem. Soc. 70, 3318 (1948).
By x-ray diffraction, K. J. Palmer, M. Ballantyne, and J. A. Galvin, J. Am. Chem. Soc. 70, 906 (1948).
By osmotic pressure, G. Scatchard, A. C. Batchelder. and A. Brown, J. Am. Chem. Soc. 68, 2320 (1046).
Sum of atomic weights.
Dow Styron, kindly supplied in solid form by A. M. Bueche, Cornell University; value quoted is turbidity of 0.5 percent solution in toluene, determined for 436 mμ on the absolute camera (references 2, 4, 5) by J. R. McCartney. A more recent determination on the same camera by E. W. Anacker gave 0.00274.
From 90° scattering, 436 mμ, in apparatus similar to ours; P. M. Doty (private communication).
By transmission at 436 mμ, P. M. Doty (private communication).
Average of two independent methods involving 90° scattering at 436 mμ; 0.00340 and 0.00357; B. H. Zimm (private communication). Other data in reference 6 indicate close agreement between turbidities determined from 90° scattering and from transmission measurements in Zimm’s laboratory.
From 90° scattering, 436 mμ, F. W. Billmeyer, Jr. (private communication).
P. Peyrot, 24°C and 436 mμ, Ann. d. Physik 9, 335 (1938).
Reference 6.
By electron microscope, number average.