REPORT
EEL 140 Atomic Absorption Spectrophotometer Atlanta, Georgia—0.1 ppm Cu for 1% absorption Pittsburgh, Pa.—0.03 ppm Ca for 1% absorption Philadelphia, Pa.—better than 2Â resolution for difficult to separate lines (iron and nickel) The above are actual practical results as the EEL 140 proves itself in the field. The EEL Flame Photometer uses no acetylene, no o x y g e n just natural gas and air. From a university in Long Island, N. Y.—2.5 ppm Na full scale (.025 ppm 1 scale division) —5.0 ppm Κ full scale (.05 ppm 1 scale division) —40 ppm Ca full scale (.4 ppm 1 scale division)
EEL Flame Photometer
For more information on these and other EEL instruments, contact your nearest
(FK
FISHER SCIENTIFIC CO. or VAN WATERS & ROGERS, INC. sales offices
INTERNATIONAL SALES ASSOCIATES 115 EAST MAPLE AVE., LANGHORNE, PA. (215) SK7-9874 See Buyers' Guide for all products/sales offices. Circle No. 54 on Readers' Service Card
evapoRaTe from one flask . . . 4 f l a s k s . . . 50 test tubes* . . . any way you need** . . . with the
NUTATING EVAPORATOR SYSTEM
A is set with its transmission axis parallel to the minor axes of the elliptical polarizations establishing equal illuminations of the two fields. S2 serves as a mask to block the extraordinary beams from P . An achromatic lens L 2 images S 2 on the entrance slit S 3 of a spectro scope. The two spectra correspond ing to the split polarizer are ob served visually or photographically and exhibit equal brightness. The presence of a circularly dichroic sample results in increasing the ellipticity of one of the beams and decreasing t h a t of the other by an amount equal to the ellipticity due to dichroism; this changes the rela tive illumination of the two spec tra. The angle through which the polarizer must be rotated in order to restore equal brightness of the two spectra at a given wavelength is equal to the ellipticity due to the sample at t h a t same wave length. A series of observations or photographic plates are made for several settings of the polarizer and the spectra are analyzed to locate wavelengths for which the elliptic ity due to sample dichroism is equal to the polarizer setting. I t is im portant to note t h a t results ob tained in this manner should be corrected for errors due to sample rotation and to deviation of phase retardations of the rhomb from quarter-wave. Measured and true ellipticities, Θ' and Θ, are related by the expression: = θ sin δ -f- α cos δ
Versatility is only half the story. Look at the efficiency of the unique vertical design and 'nutating' agitation— • you can fill flasks to 80% of capacity - up to 4000 ml. in one flask • you can forget about contamination and leaking— all liquid and vapor handling components are glass, with no rotating joints • you get maximum evaporation rates — unchanged throughout the run • you get minimum reflux —vapor doesn't condense until it leaves the vacuum jacketed transfer tube » you get true continuous feed and continuous re moval of the condensate •these are our standard manifolds •custom manifolds can be designed for just about any application
YORK INSTRUMENT CORP. 55 W. 42nd St. / New York, Ν. Υ. 10036 Circle No. 178 on Readers' Service Card 52 A
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ANALYTICAL CHEMISTRY
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where α represents optical rotation due to the sample and 8 the phase retardation due to the rhomb. Modern
Methods
No significant developments in the field of circular dichroism in strumentation took place for nearly two decades after the publication of Kuhn and Braun. Mitchell and Cormack (SO) adapted, in 1932, a modification of Bruhat's method using photographic techniques of measurement. However, the a p paratus described by Kuhn and Braun remained the only useful ap paratus for circular dichroism measurement in the ultraviolet region. With the advent of photo electric techniques several experi-
