NEW CATHODE RAY OSCILLOSCOPE
i the EDITORS column
Possesses All the Features Essential for Tests and Demonstrations CONDENSED SPECIFICATIONS S e n s i t i v i t y . V o r t i c a l a n d H o r i z o n t a l AXOH: Direct 1Γ> ΓΠΙΗ v n l t n / i n c h Full Gain O.G ΓΠΙΗ voll.n/inch
L.T. Hallett, Editor
I n p u t I m p e d a n c e , V e r t i c a l a n d H o r i z o n t a l ΛΧΟΗ: Direct
^ALIHKATIN'G
TIIERMOMKTKKS
illld
( -^ thermocouples a n d developing more precise methods for measuring high and low temperatures is a con tinuing research function a t t h e National Bureau of Standards. P l a t i n u m resistance thermom eters are calibrated over the range of —182.97 to + 6 3 0 . 5 ° C. N B S studies of a new type show promise of extending the range to ΙΟΟΙί" C There a r e three major types of platinum resistance thermometers in use. The long stem, about 18" long, is used up to 500° C. when en closed in glass and u p to 650° C when enclosed in quartz. T h e lower limit is —182.97° C. T h e sensing element consists of a helix of plat inum wire wound on a sup-porting frame of mica. I n t h e new type, the platinum wires a r c threaded through synthetic sapphire disks. This has a drift of less than 0 . 0 0 1 ° / hr. a t 1000° C. T h e stem type is calibrated a t t h e boiling point of oxygen ( — 182.97° C ) , water, a n d sulfur (444.6° C ) . T h e zinc point (419..r)0r,° C.) m a y replace the sul fur point as if is more reproducible. T h e capsule type, about 2 " long, has a sensing element similar to the stem type. T h e usual t e m p e r a t u r e range for this type is 10° Κ (—2(53" Ο.) to 300° C. These are calibrated a t the triple point, steam point, and near 50" C. and are checked against N B S s t a n d a r d thermometers a t other points. Mueller type bridges are used to calibrate these. T h e calorimetric t y p e has a coil wound on a flat strip of mica en closed in a thin metal sheath. T h i s type has a rapid thermal response. Efforts are being made to a u t o m a t e the calibration procedures. Thermocouple*. N B S calibrates thermocouples over t h e range of —190 to -f 1100" C. T h e reference points a r e t h e freezing points of
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Amplifier
0.5 metf., 20 i n m f
S w e e p F r e q u e n c y K a n Re OfwratinK Vollnfto Dimensions Shipping Weight
10 cps t o (i() k c 10fi-120
v o l U , 1 M>/60 cycle A . C . H >x 1 Ί ' jX IH,!\ ·ζ i n c h e s Λ2 pntindH
No. 2167
2167. CATHODE-RAY OSCILLOSCOPE. This is a generalpurpose instrument intended for routine laboratory tests and classroom demonstrations. Extensive field testing has proved it to be well suited to the requirements of colleges, technical schools, and high schools. Students will quickly understand the function of all the controls, and the high-grade components and careful workmanship assure long reliable service. The 5-inch cathode-ray tube employs electrostatic deflection and focus, and is operated a t an accelerating potential of about 1200 volts. Post-deflection acceleration increases its brilliance and sensitivity. Instructions are included.
Euch $158.50
THE WELCH SCIENTIFIC COMPANY ESTABLISHED 1 8 8 0
1515 Sedgwick St., Dept. A-1, CHICAGO 10, ILL, U.S.A.
THIS VERSATILE P-K LABORATORY BLENDER PRE-BLENDS, DISPERSES LIQUIDS, GRANULATES If you have any liquid-solids or solidsolid blending requirements, consider the P-K Liquid-Solids Blender. It's a fast, efficient and extremely versatile laboratory tool. With it, you'll And most blending operations can be accom plished In I to 5 minutes, achieving a uniformity not attainable with other types of mixing equipment. 3 Different Blending Actions
Gentle Precision Blending. Unique "Twin-Shell" tumbling action will not cause attrition of even the most delicate crystals. Intensive Mixing of Hard-to-Blend Dry Solids, Exclusive "rabbit ear" dispersion blades on rapidly revolving bar break up agglomerates. Liquid Solids Blending. Disperses and
IN JUST MINUTES
blends, uniformly, liquids of any viscos ity with dry solids. (Blends from Vi% liquids by weight to whatever percent age solids can absorb and still remain a solid.) Liquid is introduced into hol low shaft of revolving bar by gravity or pump. Then, flung outward from dis persion discs into the tumbling mass of dry materials. P-K Liquid Solids Laboratory Blend ers are available in 8- and 16-qt. capaci ties, in transparent lucile or stainless steel. For complete technical informa tion and prices, write to P-K's Chemical and Process Equipment Division, L'L'ii Hanson St., East Stroudsburg, Penna.
Patterson • § ) Kelley
Circle No. 86 on Readers' Service Card
VOL. 33, NO. 7, JUNE 1961
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EDITOR'S COLUMN
gold (1063° C ) , silver (960.8° C ) , antimony (630.5° C.) and zinc 419.5° C ) . These metals, espe cially gold and silver, must be ex tremely pure. Depending on the degree of ac curacy required and the range covered, thermocouples are com pared with standard resistance ther mometers, standard platinum ther mocouples, or calibrated at the fixed points mentioned. NBS also calibrates thermocouple materials such as wires and poten tiometers and supplies standard samples of various metals for use as freezing point standards. In calibrating in the range of 0 to 1450° C , platinum and plati num-rhodium thermocouples are used. Base metal alloys are used to cover less extreme ranges, par ticularly at lower temperatures where the e.m.f. of the platinum type is low. A variety of liquid baths is used in the temperature range from —190 to 538° C. Baths consist of liquid nitrogen and liquid oxygen ( —190 to —140° C.) ; liquid nitrogen-cooled baths containing carbon tetrachloride-chloroform, chloroformmethylene chloride-ethyl bromide, irans-dichloro ethylene, and trichloroethylene ( — 140 to 0° C.) ; water (0 to 100° C.) ; oil (100 to 300° C.) ; and liquid tin (538° C ) . NBS is studying new combina tions such as iridium-rhodium and tungsten-rhenium to extend the upper limit to 2000° C. NBS is working in the range of — 183 to - 2 5 3 ° C. (90 to 20° K) to provide higher precision and to pro vide a calibration service for sec ondary thermometers in the 20 to 2° Κ range. Although gas thermom eters may be used for calibrating below 90° K, they are impractical for regular use and so platinum re sistance types are used. These work well from 90 to 11° K. To calibrate in the 20 to 2° Κ range, NBS has studied changes in the velocity of sound in helium. Carbon and germanium resistors are promising secondary thermom eters in this range.
Pediçhron lniorliroii Pat. App. for.
for convenient, precise interval timing ·< Operates any standard stop watch by means of electrical foot switch — simple, durable, adjustable, instantaneous. An automatic resets timer (up to 9999.9 seconds in 1/10 seconds) with numerical readout. Automatic return to zero.
Pedichron each $33.75 (stop watch not included)
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Autochron each $ 7 0 . 0 0 (optiona foot switch also available)
available from your dealer
Clay-Adams
N e w York 10, Ν . Υ . Circle No. 41 on Reader»' Service Card
HIGH PERFORMANCE MODEL 15A
GAS CHROMATOGRAPH priced from $680 YOUR BEST CHOICE IN G A S C H R O M A T O G R A P H Y • Wide temperature range, to 300°C. To 350°C at small extra cost. ' Highest performance, with choice of 2 or 4 element filament detectors, or thermistor detectors. • Extremely stable — either manual temperature control or automatic electronic temperature control. • Reproducible sampling with precision gas sample valve. • Programmed column attachment. • Prefractionation, pre-concentration, column switching. • Two column series system. ' Independently controlled boost heaters for injection block and sample outlet fittings. • Highest quality construction, low maintenance. WRITE FOR ADDITIONAL INFORMATION.
LOENCO
, 2092
NORTH
LINCOLN
LOE ENGINEERING COMPANY AVENUE, ALTADENA, CALIFORNIA
Circle No. 72 oa Readers' Service Card VOL. 33, NO. 7, JUNE 1961
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