INSTRUMENTATION A mass spectrometer with optimum resolu lion i n the "biochemical" range. up :" A"""":l.".l lo mass 100, lor analysis of isotopic and G U I I I ~ I G A gas ...:"'..""" I I I I A I U I C ~ , IS u=sbIIueu ^ _ _ _ I ^"^" "
bg Ralph H.M&ller
A of the Journalgracious gesture marked the October issue the Optical Amaica and many of
Society of
of our readers have undoubtedly profited from its perusal. The entire issue is dedicated to A. H. Pfund of the Johns Hopkins University and contains 23 papers contributed by former students, associates, and colleagues. The issue marks Professor Pfund's formal retirement from teaching. His influence has extended fax beyond the immediate-field of optics in which he was so active. Much that we analysts find of interest and utility in infrared, radiometry, and re lated optical techniques stems from his investigations. The
Figure 1
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the Continent, but, as this happy occasion has demonstrated, there is no dearth of worthy subjects. Mass spectrometers
Process & Instruments, 60 Greenpoint Ave., Brooklyn 22, N. Y., is engaged in the design and manufacture of custombuilt instruments and equipment, including multichannel oscillographs, stimulators for nerve shock research, DC feedback amplifiers, birefringence of flow apparatus, and falling drop apparatus for heavy water analysis. It also builds mass spectrometers to customer specifications for isotopic
. INSTRUMENTATION
The ”standard of excellence” in fine constant temperature equipment.
The manufacturer’s certificate goes with every Freas oven. It guarantees the
Five-Year Guardntee, far heating unit and thermostat Hydraulic Thermostat, sensitive to SOC. Finger-Tip Temperature Control Nickel-Chromium Heater Bank All-Metal Welded Cabinets Glass Wool Inrulation, 3” thick, in doors and walls Stainless Steel Interiors, Rustproof Iron Exteriors
Mechanical Convection models, for greatest efficiency: Forced oir circulation provider uniform heot throughout the oven, quickly and surely. Heat transfer i s accelerated, drying time i s reduced, oven loading capacity i s increased. Air velocity adiustoble between 75 and 250 feet per minute.
Dispersion Staining
Bausch & Lomb Optical Co. iepoits (De?. 3 1 ) the tlevelopment of “dispersion staining” by G. C. Crossmon -a new technique adaptable to +uidnid mici oscopic- equipment whereby the various components of a colorlew sample can be made to appear in various colors. It is achieved by passing white light from the microscope lamp through a darkfield substage lens and striking the s:tmple at a high angle. With the sample placed in .the correct immersion liquid, only certain wave lengths will enter the microscope and these will vary with the nature of the optically inhomogeneous components of the sample. According to Crossmon, the use of dyes to stain tissues or bacteria is not likely t o be supplanted, especially in those cwes where absorption of the dye is :t specific chemical characteristic of the material. I n all other respects, the technique pioniises to extend the use of the micioscope very considerably in the examiliation of foodq, ctrugs, ores, minerals, tissues, and testile fibers.
Gravity Convection models, for general use: Designed to take every advantage of temperature differentials t o speed heat transfer: Ideal far all applications not requiring the advantoger of mechanical convection, or where space i s at a premium.
A I Lt o m a t i c Spectrophotonzeter
Precisian-Freas Ovens are available in a variety of sires and in two temperature ranges. They are furnished with adiustable shelves, 0-3000 C. thermometer, Neon pilot lamp, and for 115 or 230 volts, 4.C. or D.C. current. One popular size has a heating chamber 13” wide, 14” deep, and 13” high, and i s priced as fallows: 7610-Gravity Convection, 35-1800 C..._...._.. s185*00 7614-Gravity Convection, 35-2600 C.........., Wo.00 7618-Mechanical Convection. 35-1800 C..... 400.00 7621-Mechanical Convection; 35-260D C. ... 445.00 7609-floor stand, 33” high, with shelf...... 97.50
Full Informotion o n These and Other Models Upon Request
pilot light, and meter. The units are readily removed from the instrument; interunit cabling is done with shielded rubber-covered cables fitted n ith AN connectors. These units comprise an ionization gage which measures pressure and also automatically cuts power t o the mass spectrometer when the pressure rises abol-e 0.1 micron. A circuit is also included for outgassing the ion q g e grid. -4 second unit supplies the spectrometer filament : m i 1 egulates the electron beam which ionizes the gas sample. .Itliiid unit furnishes the high potentials for accelerating ioiih of different mass. A fourth supplies the magnet curient which can be set t o several magnetic field strengths with a tap switch. Another unit contains a preamplifier consisting of an electrometer tube and high input resistor, both enclosed in an evacuated iron can. The main amplifier is a carefully shielded feedback eircuit with regulated power supply. The pumping system utilizes a two-stage mercury diffusion pump and Kelch Duoseal foiepump which are connected to the spectrometer tube through a large-bore trap immersed in n Dewar flask. The diffusion pump heater is monitored by 3 protective thermostat t o guard against failure of the cooling water supply. The glass sample manifold is mounted on u removable panel and a second Welch Duoseal pump is used for its evacuation and permits a mercury Toepler pump to transfer the gas from the ianipling bulb through :I capillary leak into the spectrometer tube.
Our report on the Instrument Society of America Conference [ASAL.CHEM.,19, 817 (1947)]mentioned a paper by R. H. Kienle and E. I. Stearns on the “Adaptation of the Automatic Spectrophotometer for Special Measurements.” This paper has been published in full [Instruments,20, 1057 (1947)l. Twenty-three modifications of this instrument are described for performing a wide range of optical measurements. This article is particularly valuable inasmuch as most of the information has been available only in letters patent.
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Corccectrorc T u b e
The Conyectron tube which we described in the Decembel column is manufactured by the Eclipse-Pioneer Division, Bencliy -%&ition C0i.p , Teterhoio, S . J. 22
