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Source is chopped at 480 c.p.s. and passed into the quartz monochromator. Light leaving monochromator is switched between reference and sample paths at 15 c.p.s.

Ultraviolet to Near-Infrared Recording spectrophotometer covers wide range ;

employs doub le -beam, single detector system

A spectrophotometer that gives a continuous transmittance record from ultraviolet to near-infrared regions has been designed by Beckman Instru­ments. Called the model DK, unit utilizes the Beckman quartz-prism monochromator. Unit has photometric accuracy of 0.3%.

Core of the DK's design is utilization of the double-beam optical principle with a single quartz monochromator.

Spectrophotometer records per cent-trans· mittance directly on strip-recorder, left

This is accomplished by a system of ro­tating mirrors. Another feature of the instrument is that one detector picks up signals from both sample and reference cells. Consequently, even if response of detector is different at different

wavelengths, ratio of the signals from reference and sample paths are the same. Moreover, company says use of only one detector in the light path al­lows for simplicity in electronic circuit design.

For use in the near-infrared region, instrument employs a lead sulfide de­tector. Beckman claims that this is the first spectrophotometer to utilize the lead sulphide unit. A hydrogen dis­charge lamp and photomultiplier detec­tor are used in the ultraviolet region.

Unit records percent-transmittance versus wavelength continuously over the range 220 to 2700 πΐμ.. Scanning speeds for the entire 220 to 2700 τημ range can be 5, 15, 50, 150, or 500 min. Maximum speed in the near-infrared region is approximately 1.5 min., in the ultraviolet region—2.5 min., and in the visible region—40 seconds. High speed is recommended for samples without important fine structure and for quick explorations; medium speeds for high resolution with fast results; low speeds for utmost resolution and photometric accuracy.

In the DK spectrophotometer, source light is first chopped to eliminate effects of stray light at 480 c.p.s. (frequency allowing maximum signal-to-noise ratio with lead sulfide detector) and passed into the quartz monochromator. Light passing out of monochromator slit is reflected alternately through sample and reference cells by a mirror that ro­tates at rate of 15 c.p.s. One detector (either photomultiplier or lead sulfide)

picks up signals alternately from both reference and sample cells. Signals are amplified by an audio-type electronic amplifier.

At the same time that mirror system transmits signals to detector, a commu­tator, rotating at the same rate, sorts the signals into the reference and sample circuits.

Rectified sample voltage is sent to a recorder servo amplifier and is balanced by a corresponding voltage from a re­corder slide wire which also has the pen attached to it. Moving of the slide wire and balancing of voltages are accom­plished by the recorder servo amplifier and motor.

Rectified reference voltage is sent to a slit servo amplifier and also to the top of the recorder slide wire. Reference demodulator voltage to the slit servo is amplified and drives the slits open or closed to maintain a constant 100% reference voltage out of the reference demodulator.

Reference voltage from the demodu­lator is also applied to the top of the recorder slide wire resistance. Conse­quently, company says, variations in the source light as well as variations in detector sensitivity or detector aging do not effect the over-all results of data since both sample and reference signals will fluctuate at the same proportionate rate.

For percent transmittance, sample voltage is divided by reference voltage in a servo divider.

Beckman says that flexibility of op­eration has been a major design con­sideration. Wavelength dial of instru­ment can be operated manually while recorder indicates at every instant, sim­plifying location and measurement of absorption peaks. Wavelength drive can also be disengaged and recorder left on, allowing transmittance to be plotted against time for kinematic studies. Wavelength and slit positions can be observed at every instant on panel dials. - Ε 1

Filter Absorbs Low Activity Solutions of Radioactive Liquids

Nuclear liquid filter, portable labo­ratory type, has been developed by Atomic Energy Waste Disposal Service to absorb and concentrate dilute low activity solutions of radioactive liquids with ion-exchange resins. Unit in­cludes filter resins in cartridge form, built-in shielding and effluent hold-up tank, and an indicator section to show whether the effluent is basic or acidic.

Radioactive liquid is poured into cartridge feed reservoir. As the liquid passes through the cartridge it is de­contaminated and flows into an effluent hold-up tank.

C H E M I C A L A N D E N G I N E E R I N G N E W S 2646

Volume of radioactive liquid mate­rial may be from a few gallons up to many thousands with a single cartridge, company says. In general volume to be decontaminated depends upon concen­tration of the total ions in the liquid.

Some of the radioactive liquid mate­rial that was decontaminated by the filter are Cs137 , Sr90, Co60, Ni63, Ru106, Ce3 4 4 , S35, C14, and fission products, according to Atomic Energy Waste Dis­posal Service. Ε 2

• Manometric blood gas apparatus, called Thorn as-VanSlyke Magne-Matic model, is available from Arthur H. Thomas. Unit produces agitation by a magnetically driven stirring bar in the

' extraction chamber. Chamber is held stationary and constantly vertical, per­mitting rapid adjustment of the menis­cus, and convenient addition of re­agents. Other innovations include: ball-and-socket ground glass joints, built-in automatic timer, corrosion re­sistant housing of Formica and stainless steel, and acid-resistant hardwood base with trough for spilled mercurv.

1 3

Tracerlab Designs Secdied Automatic Flow Counter

Tracerlab's flow counter which accommo­dates up to 25 samples, makes possible the obtaining of automatic radioassays with a windowless Geiger or proportional coun­ter. Unit keeps all samples under gas flow at all times and accepts samples up to l7/8 in. diameter and Vie in. high. In­strument may be set so that each of the samples is counted one, two, three or four times or more. Switch on control panel en­ables by-passing any number of samples and to advance index accordingly. Unit has over-all accuracy of about 1%; resolv­ing time for Geiger counting of approxi­mately 150 microseconds Ε 4

For further information on any item mentioned here, see coupon

on page 2648

Years Ahead BECKMAN RESEARCH INFRARED

SPECTROPHOTOMETER For those who require the utmost in accu­racy and resolving power, the Beckman Model 1R-3 is the unquestioned choice. . Experience has shown conclusively that the IR-3 outperforms all commercial instru­ments with respect to resolving power, photometric accuracy, wavelength accuracy, freedom from st^y light and elimination of background absorptions.

Single-beam double-monochromator. Design perfection achieves very nearly theoretical resolution. Stray light is absolutely undetectable at 15 microns even with the excep­tional one-tenth of one percent measuring sensitivity of the Beckman IR-3.

Background absorptions eliminated. The entire optical path of the IR-3 can be evacuated to completely eliminate back­ground absorptions from water vapor and carbon dioxide. Liquid and gas cell compartments in both entrance and exit beams are separately sealed so that cells can be changed without affecting the vacuum in the rest of the system. All optical elements and samples are held at a constant temperature by means of circulating water and thermostat-controlled bath.

True transmittance recording through Memory Stand­ardization. No cell matching. Wavelength accuracy, 5 τημ; wavelength precision, 1 m/x.

Select an instrument today that will do tomorrow's jobs. See your Beckman Field Representative about the superlative IR-3

or write for Data File 93-d3

CUi^UUOK-B E C K M A N I N S T R U M E N T S , I N C . F U L L E R ' T O N 1 , C A L I F O R N I A

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B e c k ma η

PHYSICAL CHEMIST—Ph.D. Thirteen years experience in research a.aad production develop­ment, especially phospha-fcizing, pickling, hot dip galvanizing, corrosion control and protection. Would like position in research and development, inorganic or oil industry. Languages. Anton Urmanczy, Room 600,62 W. 45th St., New York, Ν. Υ.

SALES OR DEVELOPMENT CHEMICALS or Synthetics Anywhere. 27, married. Four years experience fine chemical sales midwest area. Box 602-L-6, C. & E. 1ST., Easton, Pa.

AGRICULTURAL CIHEMIST (ANALYTI­CAL)—Belgian University. Diversified experience. 4 languages. First papers, single, age 54. Loca­tion immaterial. Investigation, control. Box 603-F-6, C. & E. 1ST., Easton, Pa.

M I S C E L L A N E O U S Advertising of Classifications Not Included i n Directories

On Preceding E*ages (Rates on "Employment Information" pase)

PUBLICATIONS SALE, WANTED

SPECIALISTS in sets, back files, chemical, sci­entific, technical journals- Get our quotation be­fore you buy or sell. Canner's Inc., Dept. CIS!., Boston 19, Massa­chusetts.

JOURNAL OF BIOLOGICAL CHEMISTRY wanted to buy back issues and volumes. Ashley, 24 E. 21, NYC (ΙΟ).

BOUGHT AND SOLO-Complete sets, short runs, and single volumes of scientific periodicals— in all languages. Walter J. Johnson, Inc., 125 East 23rd St., N.Y. 10, N.Y.

BUSINESS OPPORTUNITIES

ACTIVE PARTNERSHIP AVAILABLE IN PHILADELPHIA—for ciiemist or chemical engi­neer with management experience. Successful firm specializing in household chemicals, in­secticides, etc. Partner -wishes to sell $15,000 to $20,000 of his share as h i s services are needed in associated firm. Box 900-L—6, C. & E. 2SL, Easton, Pa.

TRANSLATIONS

TRANSLATIONS—Articles translated from Japanese by trained cht-emist. Quick, accurate, reasonable rate. Box 900-N-5, C. & E. 3*., Easton, Pa.

EQUIPMENT

(Continued from page 2647)

• Polyvinyl chloride blowers for ex­pelling air, fumes, a_ncl gases have been developed by Industrial Fabricators. Impeller blade is also fabricated of plas­tic with threaded spinaer cap aerody-namically balanced. Line of blowers includes capacities of 500, 1500, and 4300 c.f.m. Ε 5

• Metal detector, type GP, by General Electric, consists of: two main compo­nents, a control cabinet and an inspec­tion coil. The detector detects metal by employing the effect of the metal par­ticle on the characteristics of an induc­tance-bridge circuit- Coils which make up the inspection uaiit are elements of this bridge circuit- A metal particle coming into the inspection aperture causes the bridge to "become unbalanced electrically. The output of the birdge is then amplified artel is used to operate an alarm or control Ε 6

INDEX TO ADVERTISERS

Ace Glass, Inc 2664 American-British Chemical Supplies,

Inc 2642 Analytical Chemistry 2655 Arapahoe Special Products, Inc 2600 Archer-Daniels-Midland Co 2560 Atlantic Refining Co 2564 Atlas Powder Co 2573

Baker & Adamson Chemicals, General Chemical Div., Allied Chemical & Dye Corp 2619

Barnstead Still & Sterilizer Co 2626 Beckman Instruments, Inc 2647 Bronwill Scientific, Inc 2635 Brown Co 2651 Buffalo Meter Co 2558

Carbide & Carbon Chemicals Co., A Division of Union Carbide & Car­bon Corp 2571:2645

Climax Molybdenum Co 2561 Colorado Fuel & Iron Corp., Wick-

wire Spencer Steel Div 2563 Columbia-Southern Chemical Corp.. 2633

Distillation Products Industries, Div. Eastman Kodak Co 2664

Dorward & Sons Co 2664 Dow Chemical Co 2627:4th Cover du Pont de Nemours & Co. (Inc.),

E. 1 2591 Durez Plastics & Chemicals, Inc 2653

Fritzsche Brothers, Inc 2638 Fulton Bag & Cotton Mills 2641

General American Transportation Corp . 2556

Hercules Powder Co. Inc 2637 Heyden Chemical Corp 2554 Hooker Electrochemical Co 2575

Kay-Fries Chemicals, Inc 2642 Kontes Glass Co 2562 Laboratory Construction Co 2644

Mathieson Chemical Corp 2578

Monsanto Chemical C o . . . .2559:2580-2581

Oronite Chemical Co 2649

Patterson-Kelley Co. Inc , 2588

Permutit Co 2631

Quaker Oats Co 2595

Reichhold Chemicals, Inc 3rd Cover Reinhold Publishing Corp 2655 Rohm & Haas Co 2622-2623

Shell Chemical Corp 2nd Cover Sorensen & Co 2636 Southwestern Engineering Company. . 2654

Union Carbide & Carbon Corp., Car­bide & Carbon Chemicals Div. 2571:2645

U. S. Testing Company 2553

Victor Chemical Works 2589

West Virginia Pulp & Paper Co., Poly-chemicals Div 2577:2654

Wickwire Spencer Steel Div., Colo­rado Fuel & Iron Corp 2563

Wyandotte Chemicals Corp 2593

DIRECTORY

Chemicals Exchange 2656 Arapahoe Chemicals, Inc. Bersworth Chemical Co. Fine Organics, Inc. Humphrey-Wilkinson, Inc. Metalectro Corp. Nuclear Instruments & Chemical Corp. Pierce Chemical Co. Sapon Laboratories Williams & Co., C. K.

Equipment M a r t 2657 American Phosphate Co. Microchemical Specialties Co. Pereny Equipment Co. Sethco Co. Uehling Instrument Co. Wellworth Trading Co.

Technical Services 2657 Aries & Associates, R. S. Bethlehem Apparatus Co. Inc. Bjorksten Research Laboratories Evans Research & Development Corp. Food Research Laboratories, Inc. Leberco Laboratories Truesdail Laboratories, Inc. Wisconsin Alumni Research Foundation

REINHOLD PUBLISHING CORPORATION Advertising Management for the American Chemical Society Publications

Merald Lue, Advertising Sales Manager, American Chemical Society Publications 330 W. 42nd Street, New York 36, Ν. Y.

ADVERTISING SALES REPRESENTATIVES H. Victor Drumm, Advertising Sales Manager

New York 36—BRyant 9-4430; District Managers—James L. Conklin, A. Stuart Powell, Jr., G. S. Mullin, Robert J. Halliday

Cleveland 14—NBC Bldg., 815 Superior Ave., Ν . Ε., PRospect 1-5583; District Manager— Wm. T. Bisson

Chicago 2—111 West Washington Street, RAndolph 6-8497; G. E. Cochran, Vice-President, Reinhold Publishing Corp.; District Managers—H. Scott Leonard. Frederick C. Dorr

San Francisco 5—McDonald-Thompson, 625 Market Street, YUkon 6-0647; Roy M. McDonald Los Angeles 5—McDonald-Thompson, 3727 West Sixth Street, Dunkirk 7-5391; Ε. Τ. Thomp­

son Seattle 4—McDonald-Thompson, National Bldg., 1008 Western Ave., ELliott 3767; Harry

Abney Houston 6—McDonald-Thon? n, 3217 Montrose Blvd., LYnchburg 6711; Frank N. Vickrey Denver 2—McDonald-Thomp Colorado National Bank Building, KEystone 4-4669; Robert

H. Heidersbach

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