20 A A N A L Y T I C A L C H E M I S T R Y

9101-A2.

QUARTZ SPECTROPHOTOMETER, Beckman Photoelectric. A self-contained unit with which a wide variety of research and control work can be conducted with convenience, speed and precision. Consisting of a quartz monochromator, with light source, holder for absorption cells, twin phototubes and built-in electronic meter for translating phototube currents into direct readings of percentage transmission and density. See Cary and Beckman, "A Quartz Photoelectric Spectrophotometer," Journal of the Optical Society of America, Vol. 31, No. 11 {November, 1941), V- 682.

Monochromator. Aulocollimating type, with 30° quartz prism of selected crystal which provides high dispersion in the ultra-violet. Wavelength scale approx. 100 cm long, readable and reproducible to 0.1 mmu in the ultra-violet and to 1.0 mmu in the infrared, with a scale accuracy of 1 mmu. Optical parts rigidly mounted in a massive heat-treated iron block within a dust-proof steel case.

Slits. Protected by quartz windows, with stray light ef­fects reduced to a minimum. Simultaneously and continu­ously adjustable from 0.01 to 2.0 mm by a precision mecha­nism. Slits can not be damaged by closing too far. Full scale reading with nominal band width less than 2 mmu over all but the extreme ends of the spectrum.

Electronic Indicating Meter. A built-in potentiometer and electronic amplifier makes possible direct readings in percentage transmission and density. The switch position marked " . 1 " provides a ten-fold expansion of the trans­mission scale for more accurate readings on solutions below 10% transmission.

Light Source. A standard 32 c. p. 6-volt, tungsten lamp serves as a light source for the range 320 to 1000 mmu. A hydrogen discharge lamp is furnished for use in the ultra­violet range below 320 mmu. Lamps are mounted on self-aligning, interchangeable back-plates in the liquid-cooled, cast metal lamp housing.

Sample Holders. Absorption cells are accommodated in a removable holder which is inserted in a light-tight com­partment and is operated from the front of the instrument by means of a sliding rod. Cells and holders are available for 10, 20, 50 and 100 mm liquid lengths.

Phototubes. Two phototubes are furnished in a compart­ment which adjoins the cells. A sliding rod brings either tube into position and simultaneously switches the electrical connections. A resistor box assembly {not shown in illustra­tion), with three-position switch, is now attached to the photo­tube compartment for rapid and convenient selection of proper phototube load resistor to regulate the sensitivity for alter­nate use in transmission and flame photometry.

9101-A2. Quartz Spectrophotometer, Beckman Photoelectric, Model DU, (No. 2400), range 320 to 1000 mmu, as above described, with 6-volt tungsten lamp in liquid-cooled lamp house with interchangeable backplate, one each ultraviolet-sensitive and eesium-oxide phototubes resistor box assembly, matched set of four square fused Corex glass absorption cells for 10 mm liquid depth with covers, and 4-place holder. With dry cells for operating the meter but without 6-volt storage battery for operating the tungsten lamp and electronic tubes. Overall dimensions 32J^ inches long χ 9 inches high χ 10Κ inches wide 1,200.00

9101-B2. Ditto, Model DTJV, range 220 to 1000 mmu, identical with above but with the addition of accessories for measurements in the ultra­violet region 320 to 220 mmu consisting of one pair of matched fused silica absorption cells for 10 mm liquid depth, hydrogen discharge lamp on interchangeable backplate, and power supplv unit, 115 volts, 50/60 cycles, a .c, for maintaining the discharge at constant intensity 1,500.00

More detailed information regarding above, and also Flame Photometer, Diffuse Reflectance and Fluorescence Attachments, and Test Tube Carrier Assembly, sent upon request.

We maintain a qualified technological staff for consultation, repair and service in connection with above and similar instruments sold by us.

ARTHUR H. THOMAS COMPANY RETAIL—WHOLESALE—EXPORT

LABORATORY APPARATUS AND REAGENTS WEST WASHINGTON SQUARE, PHILADELPHIA 5, PA., U. S. A.

Cable Address "Balance," Philadelphia

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