Reviewing 1 960, theWORTH INGTON

BIOCHEMICALI CORPORATION

wishes to callattention to the

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worthingtonBIOCHEMICAL CORPORATIONFREEHOLD 1, NEW JERSEY

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d-c voltage; and 750 mv (max.) ford-c current. (Mid-Eastern Electronics,Inc., Dept. Sci913, 32 Commerce St.,Springfield, N.J.)

THERMOMETER ?- -m,A

Nwew ProductsThe infornmationz reported here is obtainted from

manufacturers and from other sources consideredto be reliable. Neither Science nor the writer as-sunies responisibility for the accuracy of the in-formationi. A coupont for uise in mailing inzquiriesconicernintg the iteins listed is inicluded in the postcar-d insert. Circle the departmnent number of theitems ini which iou are imiterested oni this coupon.

* VARIABLE-FREQUENCY power sourcefurnishes 50 watts with amplitude stabil-ity said to be better than --0.01 percentand harmonic distortion 0.1 percent.Voltage is continuously adjustable to1500 volts and current to 12 amp. Fre-quency range is 20 to 20,000 cy/sec.(Krohn-Hite Corp., Dept. Sci900, 580Massachusetts Ave., Cambridge 39,Mass.)

* STANDARD TAPER STOPPER with Teflonsleeve is claimed not to bind, stick, orfreeze. Eight different sizes are offered.The 11/2- to 2-mm-thick Teflon sleeveis pernianently attached to the hardborosilicate glass body. (Scientific GlassApparatus Co., Dept. Sci903, Bloom-field, N.J.)

* FLUXMETER of nuclear-magnetic-reso-nance type measures uniform magneticfields in the range 1 to 52 kgauss. Fre-quency instabilities caused by varyingexternal components or probe positionare eliminated by buffering the probecompletely from frequency determiningcircuitry. Standard probe cable lengthis 6 ft, but extensions of 50 ft or morecan be supplied. (Varian Associates,Dept. Sci906, 611 Hansen Way, PaloAlto, Calif.)

* FRACTION COLLECTORS in 12 modelsprovide timed collection, volumetricsiphon collection, or timed, siphon anddrop-counting collection in one unit.Any of the three collecting units maybe used with any of three turntables:a 19-in. model for 120 tubes, a 24-in.model for 240 tubes, and a sectionalmodel for six sets of 40 tubes. Eachsection of the latter is individually re-movable. Completely refrigerated as-seniblies are also available. (BuchlerInstruments, Inc., Dept. Sci910, 514West 147 St., New York 31, N.Y.)

* METER CALIBRATOR is a self-contained,completely solid-state instrument. Volt-age ranges are 0-2.5, 0-5, 0-10, 0-25,0-50, 0-100, 0-250, and 0-500, for a-cand d-c. Direct current range is 100 Mato 1 amp. Resistance range is 25 ohmsto 2.5 megohms. Accuracy is said tobe +0.5 percent of full scale on allranges between 65 and 90°F. Outputratings are: 50 ma (max.) for a-c volt-age measurements; 100 ma (max.) for

Write tor complete catalog

SCIENCE VOL. 132

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* ADIABATIC CALORIMETER measuresover a temperature range -130° to+200°C. Liquid or solid samples of 0.5ml volume are required. Adiabatic con-ditions are maintained over the operat-ing temperature range by means of au-tomatic temperature control of isother-mal and environmental shields sur-rounding the calorimeter. (AppliedPhysics Corp., Dept. Sci908, 2724 So.Peck Rd., Monrovia, Calif.)

* pH METER of the glass-electrode typeis said to have an accuracy of +0.05percent. A 6-in. scale covers the rangefrom 0 to 14 pH. Temperature compen-sation is continuously adjustable be-tween 0° and 100'C. High resistanceglass electrodes are employed against asilver chloride reference electrode. Thisinstrument is said to remain unaffectedin its reading by mains fluctuations of± 10 percent. (New England ScientificInstruments Co., Dept. Sci909, 238Main St., Cambridge 42, Mass.)

* TUNNEL-DIODE-CURVE TRACER permitsthe study of forward characteristics oftunnel diodes including gallium ar-senide types. Curves are displayed onany sensitive oscilloscope. Through theuse of an external decade box, avail-able as an accessory, it is possible toread actual negative resistance of thediode at any point on the curve. (TexasInstruments, Inc., Dept. Sci912, 3609Buffalo Speedway, Houston 6, Tex.)

* VARIABLE LEAK provides conductancevariation over a range greater than 10",from 10 cm'/sec to less than 10-cm3/sec for noncorrosive gas. The de-vice is bakeable for extended periods at450'C. The leak is said to be operablesafely at external pressures to 400lb/in.! A driving torque of 12 in. ozis said to be sufficient to seal the leakat 500 lb/in.2 inlet pressure. (Gran-ville-Phillips Co., Dept. Sci917, Box198, Pullman, Wash.)

* TRANSISTOR ANALYZER for demonstra-tion purposes mounts components on aclear plastic plate 3/16 in. thick. Anygeneral-purpose transistor may be used.Common emitter, common base, andcommon collector configurations canbe demonstrated. Frequency limitationscan also be shown. Available accessoriesinclude meters, audio oscillators, con-nectors, and clips. (Central ScientificCo., Dept. Sci918, 1700 Irving ParkRd., Chicago, Ill.)

* THERMOMETER allows measurementof surface temperature without con-tact. The instrument consists of a re-sistance sensing head that is positionedabout 0.003 in. from the surface to bemeasured. A parabolic reflector behindthe resistance element is said to com-pensate errors. Temperature to 450°F2 DECEMBER 1960

The Datagraph Printer attaches quickly to the DU and greatly increases its usefulness

make your DUdo its own

data 'plottingYour DU Spectrophotometer can do its own data plotting if

you attach C.I.C.'s new DATAGRAPH PRINTER to it (assem-bly time: 20 minutes!). The wavelength knob on the DU be-comes a chart drive and the potentiometer knob moves the pen.Set each knob as you normally do, press the print bar and youhave a permanent record of absorbance. You can record ab-sorbances of several samples on a single sheet with the DATA-GRAPH PRINTER or quickly plot a complete spectrum.

The DATAGRAPH PRINTER is not onlya timesaver but eliminates o:of errors - those which opotentiometer and wavelennotebook. The simple addiGRAPH PRINTER canvalue of the DU Spectrophcomplete details.

ne important source NEW5LRiccur in transposingIgth readings to theltion of the DATA-.-almost double theotometer. Write for

For more informationon the Datagraph Printer and other CICproducts, write for the CIC Newsletter.

CONN ECTICUT INSTRUMENTCORPORATION

DANBURY ROAD, WILTON, CONNECTICUT1711

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is measured. Operation is from a singleflashlight battery and temperature indi-cates directly. Hand-held and panel-mounted models are available. (GelmanInstrument Co., Dept. Sci914, 106Main St., Chelsea, Mich.)

* SYNCHRO INDICATOR for nonambigu-ous remote indication of linear or angu-lar position combines a 1: 1 and a36: 1 indicator. A separate receiver isgeared to each pair of concentric dialpointers. Reading accuracy is said to be±0.03 deg. Resetting and nonresettingmodels are available. (Scientific-AtlantaInc., Dept. Sci922, Atlanta, Ga.)

* MICROMANOMETER reads directly dif-ferential pressures as low as 0.0001mm-Hg. Eight full-scale ranges from0.01 to 30 mm-Hg are selected by afront-panel switch. In addition to visualreadout, both phase sensitive a-c andpolarized d-c electrical outputs are pro-vided. Response time when using theelectrical outputs is said to be of theorder of 10 msec and accuracy of com-parison of two pressures +0.05 percentor better. Low absolute pressures maybe measured by connecting one pressureport directly to a vacuum pump.(Trans-Sonics, Inc., Dept. Sci915, P.O.Box 328, Lexington 73, Mass.)

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now Government surplus due todesign change. A lifetime bat-tery with no known limit ofservice (over 500 recharges ontest without loss of capacity).

Other features: Virtually indestructible, com-pact & lightweight, withstands heavy shockand vibration. Flat voltage curve during dis-charge retains charge year or more, highdischarge rate up to 50 amps, for this cell, nocorrosive fumes to harm clothing or equipment,spill-proof construction, discharge in any posi-tion, indefinite storage without deterioration,operates in temperatures -600 F. to +2000 F.Each cell is approx. 4 ampere hour capacity.Nominal voltage per cell is 1.2 volts. Cell size6" H. x 2" W. x 1/2" T. Wt. 6 oz. ea. UsesPotassium-Hydroxide (30%) electrolyte. Negligi-ble loss during lifetime service. Add only dis-tilled water once a year. A fraction of Govern-ment cost.Used Test Cells ........... 1.95 ea. PostpaidBrand New Cells ........... 2.95 ea. Postpaid6 V. Battery (5 cells in stainless

steel case) ...... Used $10.00 New $15.0012 V. Battery (10 cells in stainless

steel case) ...... Used $20.00 New $30.0024 V. Battery (20 cells in stainless

steel case) ...... Used $40.00 New $60.006 ampere hour cells, size 41/2" H. x 2%" W. x3¾4" T. . Used test cells $3.50 NEW cells $4.95Plastic battery cases may have slight cracks-repaired easily with household cement or youmay add 250 to price to insure uncracked case.ESSE RADIO COMPANY, Dept. Si42 W. South Street Indianapolis 25, Indiana

1: 0.07 or a 1: 0.09 object to imageratio. A variety of camera backs slideinto position on the mounting plateswith a detant mechanism defining eitherthree or ten equally spaced positions.(Analab Instrument Corp., Dept. Sci-925, 30 Canfield Rd., Cedar Grove,N.J.)

* WHEATSTONE BRIDGE measures from1 ohm to 100 megohms in eight ranges.Accuracy is said to be ±0.05 percentand indicator sensitivity 1 mv full scalerepresenting 1 percent bridge unbalancefrom 5 ohms to 50 megohms. The read-out amplifier is a transistorized chopperamplifier. Power supplies for operationon 117 volts 60 cy/sec power are builtinto the instrument. (Calibration Stand-ards Corp., Dept. Sci923, Pomona,Calif.)

* PERMEAMETER measures magnetizingforces up to 300 oer with accuracy saidto be ± 1 percent. Specimens of rec-tangular cross section up to 3 by 1 cmand 24 to 28 cm long can be tested.Features include slip-ring contacts onmoving H-coil platform and solenoiddrive for rotating H coils. Constants arederived from dimensions of the instru-ment so that calibration is not required.(Minneapolis-Honeywell Regulator Co.,Dept. Sci924, Ridge Ave. at 35th St.,Philadelphia 32, Pa.)

* REMOTE-READOUT MODULES displaysix digits, using numeral-electrode gas-discharge tubes. Models are availablethat are equipped with integral amplifi-ers, power supply for ten-line-per-digitinput or binary-decimal decoding net-works. Other combinations can be fur-nished to order. (Transistor SpecialtiesInc., Dept. Sci927, Plainview, N.Y.)

* DISPLACEMENT CALIBRATION STANDfor differential-transformer type trans-ducers consists of a vernier-type micro-meter, a nonmagnetic threaded corerod, mounting block and binding posts.Range is 0 to 1 in. and accuracy of themicrometer is said to be ± 10()0 pin.(Schaevitz Engineering, Dept. Sci928,P.O. Box 505, Camden 1, N.J.)

* POWER SUPPLY iS said to provide+0.0005 percent regulation of line andload at terminals. Voltage stability issaid to be less than 0.0002 percent plus10 uv for a 10-percent line voltagechange. Internal impedance is less than250 gohm, hum and noise level areless than 50 tuv, and output drift is+0.01 percent. Transient response is 25,usec for recovery to within 10 mv ofsteady-state voltage after applications offull load. Output voltage is continuouslyvariable to 36 volts and settable to 10mv. (Krohn-Hite Corp., Dept. Sci931,580 Massachusetts Ave., Cambridge 39,Mass.)

1714

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SPRAGUE-DAWLEY, INC.Pioneers in the development

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We are completing another newmodern colony which will doubleou. present production.The new colony building con-tains every device to insure con-tinuous production and ship-ment of guaranteed Sprague-Dawley strain albino rats.

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* MIRROR BLANK for lightweight tele-scope system consists of two fused-silicaplates separated by walls or tubes of thesame material. The ribs are permanentlysealed to the plates. Weight is reducedto half that of a solid disk. Blanks areavailable in a wide range of sizes andshapes and can be formed to order. Ac-cording to the manufacturer the blankswill accept any standard reflective coat-ing and can be ground and finished withstandard equipment. (Corning GlassWorks, Dept. Sci929, Corning, N.Y.)

* SCANNER switches sequentially digitaldata points in the form of contact clos-ures at the rate of 50,000 points persecond. Maximum switching capacity is199 points. Actuating signal is a pulseof -10 volts per minute amplitude and5 ,usec duration. The output signal maybe used for switching if the load im-pedance is 4.7 kohm or greater. Operat-ing temperature is -49' to +1310F.(Datex Corp., Dept. Sci936, 1307 S.Myrtle Ave., Monrovia, Calif.)

* ELECTRO-OPTICAL RELAY has a con-ductance on/off ratio of 1,000,000 to 1and is capable of speeds up to 100 oper-ations per second. The device includesa light source which, when excited, ac-tuates a photoconductor allowing eithera-c or d-c power to pass. "On" life issaid to be 2500 hours regardless of thenumber of switching operations. It issaid to be free of any contact noise.(Raytheon Co., Dept. Sci932, Newton58, Mass.)

* THERMAL-NOISE SOURCE derives its sig-nal from thermal agitation in a resistor.Frequency range extends more than 15octaves, including subaudible, sonic, andultrasonic. A filter network allows selec-tion of equal energy per cycle per oc-tave. (Western Electro-Acoustic Labora-tory, Dept. Sci937, 11789 San VincenteBlvd., Los Angeles 49, Calif.)

* TUNING-FORK MODULE, designed foruse with printed circuitry, measures 3/8in. in diameter and 23/8 in. long. Weightis 8 oz. Frequency range is 350 to 1 800cy/sec directly. Accuracy is said to be±0.01 percent over a moderate tem-perature range. Operating temperaturerange is -550 to +1000C. (GyrexCorp., Dept. Sci933, 3003 PennsylvaniaAve., Santa Monica, Calif.)

* VOLTAGE REFERENCE is designed forthe calibration of voltmeters operatingin the frequency range 10 to 1000 Mcy/sec at voltages from 0.5 to 300 volts.The instrument consists of an adjustablewaveguide-below-cutoff attenuator feed-ing an ultra-high-frequency vacuumthermocouple. The d-c- output of thecouple is read on an auxiliary millivolt-meter. The instruments are furnishedwith National Bureau of Standards cali-

Includes everything needed to performa wide variety of logical operations

Now Digital offers a basic selection of 500 kilocycle logic circuit packageswhich can be used to design, test and demonstrate up counters, downcounters, four-bit shift registers, decimal decoders, Gray-to-binary de-coders, two-binary-digit adders and subtracters, and other similar digitalpulse apparatus.

Graphic front panels (a Digital first) permit all logical interconnectionsto be made quickly and easily by means of handy stacking banana-jackpatch cords. And the units can be assembled and reassembled in anynumber of different combinations in the plug-in mounting panel.

Included in the Basic Kit are nine DEC Digital Test Equipment unitsone inverter, one diode nor, four flip-flops, one delay, one clock, and onepulse generator- and the necessary accessory equipment- power sup-ply, power cable, mounting panel, and one hundred patch cords. OtherBuilding Blocks from Digital's fully compatible 500 kilocycle, 5 megacycleand 10 megacycle lines can be added to increase the versatility of thisunique new kit.

-1 Complete Kit (FOB Maynard) $1038

Write for your copy ofDigital's popular newlogical operations hand-book- "DEC BuildingBlock Logic" EQUIPMENT CORPORATION

MAYNARD - MASSACHUSETTS

WEST COAST OFFICE * 8820 SEPULVEDA BOULEVARD * LOS ANGELES 45, CALIFORNIA

2 DECEMBER 1960 1715

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FREE DATA KITS& S Membrane Filtersfor nuclear applicationsand ultrafiltration

* Type A (for aqueoussolutions)

* Type UA lultrafine -for aqueous solutions)

* Type 0 (for organicsolvents)I

* Type UO (uItrafine -for organic solvents)

flexible, dry or wretSUGGESTED APPLICATIONS:1- Air filtering (cleaning air for glove-boxes; sampling laboratory or outsideair) 2- Colloidal filtration 3- Collectingradioactive samples (since radioactiveparticles stay on filter surface, meas-urements can be carried out withoutabsorption of radiation by the filter).4- Determining solids in water (analyz-ing water in reactor coolant systems).5- Retention of bacteria, rickettsiae,viruses, and other microbes.

Standard filter diameters are 20-300mm. Pore sizes are 0Ilt down to below0.005S. Type A and UA MembraneFilters are used with aqueotLs solutions;Type 0 and UO Mlembrane Filterswith solutions containing organicsolvents; Type AF Membrane Filtersare used for air and gas sampling.

Filters may be examined by ordinarylight or by electron microscope. Re-flected or transmitted light may beused. In microscopic examination byreflected light, S & S Black or GreenMembrane Filters will prove helpfulas contrasting background for whiteor slightly colored particles.For air analysis S & S Type AF

Membrane Filters (maxinmum porc size1O,t) may be used for qualitative andquantitative detection of dust particles,metals, smokes, and micro-organisms.Particles collected are in unchangedcondition on filter surface. Full infor-mation is given in the S & S MIembraneFilter Data Kit.

MAIL COUPON FOR MEMBRANE FILTER DATA KIT. ................. . . . . . . . . . . ......................................@...

Carl Schleicher & Schuell Co.543 Washington StreetKeene, New HampshireSEND FREE S & S Membrane Filter DataKit. Information on filters; apparatus. Tables,data on resistance to acids and alkalis; spec- -

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bration from 10 to 400 Mcy/ sec. Ac-cording to the manufacturer, the cali-bration will remain accurate to within± 1 percent for at least a year. (Ballan-tine Laboratories Inc., Dept. Sci934,Boonton. N.J.)

* CHROMATOGRAIlH PROTECTIVE DEVICEturns off current to thermistor or hot-wire thermnal conductivity elements ifcarrier-gas flows is interrupted. The de-vice is an automnatic pressure switch ac-tuated bx- a bellows. (F & M ScientificCorp.. Dept. Sci935. 1202 Arnold Ave.,N.C.C. Air Base. News Castle. Del.)

* SWEPT-SIGNAI GENERATORS cover infive units the L. S. C, X. and Ku bandsfrom 1 to 18 k\lJcv/sec. A conmmonposwer and ssweep supply can be usedssith any of the units. A typical unit pro-vides a power output constant within Idb over the entire S band. Frequency/time characteristic is linear within -4-4percent. Ssseep rate is adjustable be-tween 0.3 and 30 cv/sec. (Melabs Inc..Dept. Sci938. 3300 Hillsiew Ave.. PaloAlto. Calif.)

* VIBRATORY POIlISHER for metallo-graphic specimens can handle 20 sam-ples simultaneously. The flat-bottonmedpolishing bowl is supported on leafsprings and vibrated electromagnetical-ly. Amplitude of vibration and rate ofpolishing are regulated by a dial. Thepolishing operation is autoimiatic andsamples can be removed and new onesadded at anv time. Bowls are inter-changeable. (Fisher Scientific Co.. Dept.Sci939, 717 Forbes Ave.. Pittsburgh1 9. Pa.)

* IMPEDANCE BRIDGE functions as ana-c or d-c Wheatstone Bridge with range0 to 1 megohm: a modified Wheatstonecapacitance bridge. including D andDQ, with range 0 to 1(00 1, and dissi-pation factor 0 to 1L.0. It can also func-tion as a Maxwsell or Hay inductancebridge wsith ranoe 0 to 100 hv. A signalgenerator for I kcv sec excitation isprovided. Externally generated signalsfronm 60 cv to 10 kcy/sec can be intro-duced. An oscillator-amplifier accessorycontains a d-c voltage source, a 1 kcy/sec oscillator with controlled voltageoutput. an excitation amplifier, and anull-indicator amplifier. (Winslow Co.,Dept. Sci930. 701 Lehigh Ave., Union,N.J.)

* P'RESSURE CALIBRATION SYSTEM iSbased on a dead-weight system withautomatic placement of weights to coverthe range 0 to 3500 lb/in.2 in 1 lb/in.2increments. Air is automatically ad-mitted or removed from the balancemanifold until balance is reached.Weight programing arrangements rangefrom a tape device that automaticallyprograms the weight hiandler and selects

ml

CONDUCTIVITY BRIDGES

- i i ia i Industrial Instru-|111 tments offers acomplete line of

electrolytic con-ductivity bridgesfor the measure-ment and controlof solution con-

centration. Standard models are availablefor use in conductive solutions ranging fromdistilled water to concentrated acids or al-kalis, and in all temperature ranges.

CONDUCTIVITY CONTROLLERSFor steam generation,water purification,chemical processinggeneral lab work, andwherever continuousindication and/orcontrol of solutionconductivity is re-quired Industrial Instruments has a wide line otpractical instruments designed specifically forthe job. Also available are conductivity recordersin circular and strip-chart, single and multi-pointtypes as well as battery-operated units.

CONDUCTIVITY CELLS

A single source for all. your cell needs. Body~ materials in the wid-

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plete selection of cells designed to meet yourapplication requirements ... no universal com-promises. Nickel platinum, graphite, gold or tinelectrode materials as well as a comprehensiveselection of cell constants and ranges for everymeasurement application.

Write for yourpersonal copy ofour new Catalog #23.

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SCIENCE, VOL. 132

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: (City) (State): 1 Also send S & S Analytical Filter Paper

Data Kit.

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pressure manifolds and transducers, toa set of manual switches to set desiredpressure. (Gilmore Industries Inc.,Dept. Sci947, 13015 Woodland Ave.,Cleveland 10, Ohio)

* MICROWAVE ANTENNA of high-gaindielectric-rod type is capable of con-stant radiation in ambient temperatureas high as 2000°F or shock of the orderof 60 grav. The units can be suppliedwith linear or eliptical polarization overa fre.quency range 1300 to 14,000Mcy/sec. (Don-Lan Electronics, Inc.,Dept. Sci950, 1131 Olympic Blvd.,Santa Monica, Calif.)

* RESISTANCE DECADES for the multi-megohm range are available in eightmodels covering ranges from 1 to 100megohms. Accuracy is said to be ±0.1percent. Stability is said to be within+0.05 percent over the temperaturerange -50° to +80°C. Individual dec-ades are available unmounted. (Wins-low Co., Dept. Sci 940, 701 LehighAve., Union, N.J.)

* DEHYDRATOR for drying air or bottledgas is said to achieve a dew-point of-1 80°F. Regeneration does not useheat. Instead, a small portion of ex-panded dried air is used to dry the

every laboratoryhas the spaceand a jobfor the...

CHROMATOBOX®for paperchromatography

It measures only 3" x 3" x 2", and produces a 17" paper chromatogramfaster, easier, more economically than larger equipment. Uses only10 to 15 ml of solvent; quickly saturates its small atmosphere. Littlejobs done in the CHROMATOBOX leave cabinets and jars free anduncontaminated for larger jobs. Use it for solvents that damage otherapparatus. All parts are solvent resistant plastic or glass.

The low price and convenience of the CHROMATOBOXopen new opportunities to every user-

Students can be given individual prac-tice in developing chromatograms.* Lectures can be illustrated with activedemonstrations. * Test strips can be runthat were previously neglected becauseof the bother with larger equipment.* The scope of clinical laboratories canbe broadened with data given only bychromatography.

Price $10 F.O.B. Richmond, California. Dept.A.

)RESEARCH SPECIALTIES CO.RICHMOND. CALIFORNIA

1718

desiccant. The system produces up to25 ft/min of air containing less than0. 1 part per million of water vapor byvolume. (Lear Industrial Products,Dept. Sci942, 1 10 lonia Ave., NW,Grand Rapids 2, Mich.)

* X-Y RECORDER converts digital infor-mation into corresponding incrementalmotions of plotting paper and pen.Drum and pen increments are 0.01 in.in either positive or negative directions.Stepping rate of up to 200 incrementsper second can be provided. Z-axis mod-ulation, accomplished by raising andlowering the recording pen, can bemaintained at up to ten operations persecond. Positive or negative pulsesgreater than 10 volts and with risetime less than 10 1usec from source im-pedance less than 500 ohms can be usedto drive the recorder. Front panel con-trols permit manual actuation of all mo-tions. (California Computer ProductsInc., Dept. Sci926, 8714 Cleta St., Dow-ney. Calif.)

* OSMOMETER determines molecularweights up to 10,000, using a vapor-pressure method. A massive aluminumblock encased in urethane foam re-places the conventional water bath.Probes for aqueous and nonaqueoussolutions and a thermostat for 30°Cchamber temperature are provided.Others are available. (Mechrolab, Inc.,Dept. Sci941, 1062 Linda Vista Ave.,Mountain View, Calif.)

* BISTABLE AMPLIFIER conmbines amagnetic amplifier with a controlledrectifier unit. An input signal of 0.05Auw produces a 24-volt d-c output at cur-rents up to 1 amp. Response time is 22msec. Four control windings permitcomparison addition or subtraction ofup to four signals. Operating tempera-ture range is -55° to +85°C. Othercontrol-winding arrangements and out-put ratings are available. (NorbatrolElectronics Corp., Dept. Sci943, 356Collins Ave., Pittsburgh 6, Pa.)

* FLASH ILLUMINATOR for small andmicroscopic subjects uses a small xenon-filled lamp. Light can be imaged on thesubject by a conventional condensinglens system or by direct radiation. Atungsten-filament lamp of variable in-tensity located near the flash lamppermits optical line-up and focusing.Flash duration is 150 usec with 100watt/ sec input. (Edgerton, Germes-hausen & Grier, Inc., Dept. Sci944, 160Brookline Ave., Boston 15, Mass.)

* RECORDING DIFFERENTIAL REFRAC-TOMETER is said to measure index ofrefraction changes as small as 7 x 10-.Full-scale ranges as narrow as 0.0003and as broad as 0.16 are possible. Theinstrument uses the null principle and

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10 TOO MANYcgVARIABLES?

It's time to draw a line.Straighten out your cleaningproblems with

New ProductsJoshua Stern

DOI: 10.1126/science.132.3440.1710 (3440), 1710-1720.132Science

ARTICLE TOOLS http://science.sciencemag.org/content/132/3440/1710.citation

PERMISSIONS http://www.sciencemag.org/help/reprints-and-permissions

Terms of ServiceUse of this article is subject to the

is a registered trademark of AAAS.Scienceof Science, 1200 New York Avenue NW, Washington, DC 20005. The title (print ISSN 0036-8075; online ISSN 1095-9203) is published by the American Association for the AdvancementScience

Science. No claim to original U.S. Government Works.Copyright © 1960 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of

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