ORGANIC INTERMEDIATES FROM SWITZERLAND

NH2 CH3

N02

3-NitrO-o-toluidine 2-Methyl-3-nitroaniline

COOH

NOL (NH2) A COOH

5-Nitroisophthalic acid 5-Aminoisophthalic acid

NH2

α,α,α-Trifluoro-m-toluidine, 99% 3-Aminobenzotrifluoride

Isosorbide dinitrate, ISDN mixtures with lactose, etc.

CI

NO2

NO2

1 -Chloro-3,4-dinitrobenzene

NH2

CH3

CH3

2,4-Xylidine and all other isomers

Custom made intermediates against secrecy agreement For catalog, samples, technical data please contact: US-Agents: Riches-Nelson, Inc. 254 Mill Street, Greenwich, Conn. 06830 Phone: 203-869-3088 Telex: 230-96 59 39 ricnelinc Samples for commercial trade only Agents in other countries: Please inquire

SSF DOTTIKON Swiss Explosives Works Ltd. CH-5605 Dottikon/Switzerland Phone 057/4 05 55 Telex 52 694 fasex ch

Our traditional processes: - nitration - catalytic hydrogénation and other reactions

CIRCLE 20 ON READER SERVICE CARD

Technology

New instruments combine microscopy techniques Combinations of techniques are the strong points of two new instruments introduced recently at a Scanning Electron Microscopy Inc. meeting in Washington, D.C.

One, coming from Perkin-Elmer's physical electronics division, Eden Prairie, Minn., combines a scanning electron microscope (SEM), a scan­ning Auger microprobe (SAM), and an energy-dispersive electron micro-probe (EDX) in the company's PHI Model 595 Multiprobe.

The other, from International Scientific Instruments Inc., Santa Clara, Calif., combines a transmission electron microscope and a light mi­croscope in the firm's LEM-2000.

P-E expects its Multiprobe to add a new dimension to materials re­search. ISPs LEM-2000 is aimed primarily at diagnostic pathology— tissue analysis—but the company expects spin-off applications in ma­terials research as well.

Bringing the probe technologies together, P-E says, makes it possible to determine the surface and bulk composition of particles or surface features as small as 500 A. Although it's been possible to observe such features before, the company says, it hasn't been possible to distinguish their composition clearly from the background.

In operation, a sample is bom­barded by a beam of electrons, caus­ing emission of secondary electrons and chemically specific Auger elec­trons and x-ray photons. The secon­dary electrons originate in the outer few atomic layers and are processed to obtain a high-magnification image of the sample surface (SEM).

Auger electrons also come from the top two or three atomic layers. Their kinetic energy and number qualita­tively and quantitatively identify the elements present in the outer layers of the sample. Scanning the electron beam also provides the distribution of elements over a selected area (SAM).

The x-ray photons originate pri­marily farther down in the sample. Thus, their energies identify the bulk composition of the sample (EDX).

P-E points out that the Multiprobe isn't simply an SEM with an Auger and an x-ray attachment. What makes integration of the three tech­niques possible is a new electron gun that utilizes total electromagnetic beam focusing and is compact enough

Perkin-Elmer's PHI Model 595 Multiprobe combines three methods of analysis

to fit inside the electron energy ana­lyzer. Operating at beam voltages from 2 to 30 kV, it provides beam di­ameters of less than 500 A, enabling a researcher to obtain topographical maps at up to 50,000X magnifica­tion.

The Multiprobe has what P-E calls a multiple-technique analytical computer system (MACS). This, coupled with a dedicated micropro­cessor, provides for computer-di­rected system operation and auto­mated data collection, storage, and processing.

ISI's LEM-2000 does away with one of the problems encountered in specimen analysis. Ordinarily, areas of interest in a prepared specimen must be identified under a light mi­croscope. Then, exactly the same areas must be examined under an electron microscope. The problem is that the images viewed under the two modes vary greatly and are not vis­ually similar. Accurate positioning of the specimen thus can be quite diffi­cult.

The LEM-2000 uses computer control to handle this entire posi­tioning operation. The specimen is divided into as many as 100 area po­sitions in a grid. After an area of in­terest is located and photographed with light optics, the computer, which controls the staging area, automati­cally repositions the same area for viewing and photographing with the electron optics.

The ISI system has 100-kV elec­tron optics. It provides for 50X mag­nification in the light mode and 45,000X magnification in the electron mode. •

34 C&EN April 30, 1979

m

Tor dyestuffs pharmaceuticals agrochemicals perfumes photochemicals