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International's Micro Modeluniquely combines high efficiencywith low cost for micro andsemi-micro analyses. It's thepreferred tool for teachingcentrifuging techniques in manycolleges, universities andscientific laboratories.

International's Model MBis first choice forimplementing themicro-capillary method ofblood cell volume testing.With this "Quiet Test" cen-trifuge, samples spun at11,500 RPM, are ready foraccurate reading in 3 or4 minutes.

International's Clinical Modelhas long been recognized asthe most versatile centrifugein the bench-size class. Itswings more than 25 accessorycombinations at speeds up to6700 RPM.

International's Model CSCombiines CAT ecoinomy andSP, spee(d atnid ver-satilityin one all-new cabinetizedcenitr ifutge. Delix ers tip to4,730 G for rotuitineworlk: tip to 37,950 Gwith mtulti-speedl attachment.Swings horizontal, aingleand basket heads.

SCIENCE, VOL. 1321340

packardTR I-CAR B

LIQUID SCINTILLATION

SPECTROMETERS

are now

TRANSISTORIZED

ka Instaum en t Company, Inc.

Since its introduction six years ago, theTri-Carb'R' Liquid Scintillation CountingMethod has become the leading method forthe radioassay of samples containingTr-itium,Carbon-14, Sulfur-35 and other alpha- andbeta-emitters. More samples of Tritium andCarbon-14 are now being counted in theTri-Carb Spectrometer than in any otherinstrument. Look around-with hundreds ofinstallations throughout the world, there isa Tri-Carb Spectrometer near you.The Tri-Carb Method has been developing

continually-both by new sample preparationtechniques and by improvements in instru-mentation. And now the latest advance istransistorization.

Greater reliability is one of the principaladvantages gained by transistorizing the Tri-Carb Spectrometer. Both size and weightof the electionics have been reduced. Powetconsumption is appreciably lower and muchcooler operation is achieved. Line voltageregulation and over-all stability have beenimproved significantly by the transition tosolid state electionics.

In gaining these advantages no compromisehas been made in operating perfoirmance.Specific figures showing the excellent count-ing efficiencies with low backgrounds that areobtainable under various conditions and withmany types of samples are reported in theliteratur-e by numerous Tri-Carb users. Simi-lar performance is routinely achieved withthe new transistorized design.

Other new developments are broadeningthe scope of liquid scintillation counting.Improved sample prteparation techniquesnow make this the method of choice for assay-ing almost every type of sample material-proteins, carbon dioxide, tissue, lipids,tritiated watei, completely insoluble materi-als, etc. Special accessory devices have beendesigned to adapt all Tri-Carb Spectrometers,old and new, to continuous liquid flow moni-toring in applications such as column chro-matogiaphy, amino acid analysis, and traceror safety studies in plant oIr field streams.Other new Packard accessotry instruments arealso available for adapting all Tri-C'arb Spec-trometers for radioassay of the effluent fromgas chromatographs by both continuous flowand fraction collection methods.

Transistorized Tni-Car-b Spectrometers areavailable now-and at no increase in priceover the older models. They are in plroductionand we can make prompt delivery. To receivecomplete information on new transistorizedTri-Carb Spectrometer-s and new accessoryequipment as well as general information oncurrent sample preparation techniques, writeor telephone.

P. 0. Box 428-A * La Grange, Illinois * Phone HUnter 5-6330

ATLA N TA * BO STO N * LPITTSBU RGH * SAN FRAN

1368

OS A NG EL ES * NEW YORK * PHI LADE LPH IACISCO * WASHINGTON, D. C. * ZURICH, SWITZ.

SCIENCE, VOL. 132

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