Curator's Choice: A Selection of Instruments from the Museum Stores

Richard Paselk, Curator

Leitz Dialux Polarizing Microscope and Accessories

This top-level research polarizing microscope is accompanied by a very complete set of accessories, many of which can be seen on the microscope and the shelves above and below. It is set-up with a trinocular photomicrographic tube, five position nosepiece with individual centring for objectives, mechanical stage, graduated revolving stage, 2-diphragm centerable substage condenser, base lamp and synchronous rotation arm. The original case is displayed below.

This instrument was purchased for Chemistry Professor John B. Russell to pursue his studies in chemical microscopy. (Geology Professor John Longshore had a nearly identical instrument for his research in petrography.)

Use/History

The polarizing microscope is a much an optical measuring instrument as it is an instrument for the detailed examination of specimens. In addition to standard microscope optics, there is a polarizer in the condenser and another mounted in a slider in the tube above the objective, both in rotatable, graduated, mounts. The specimen is illuminated with plane polarized light, and its rotation of this light can be analyzed. The polarizing microscope is particularly useful in the study of birefringent materials such as crystals and strained non-crystalline substances. It is widely used for chemical microscopy and optical mineralogy. For further information on polarizing microscopes I recommend the pages by Dr. James Gregory McHone. In addition to a brief overview, they include extensive links to images, literature, instructions etc.

Description

The current specimen is equipped with a quintuple nosepiece with individual centering for each objective and a graduated, rotating stage with verniers, built-in illumination system, trinocular head for visual and photographic observation, and two diaphram condenser. It is displayed with a syncronizing arm conecting the polarizer and analyser (note the standard polarizing condenser and adjustment knob sitting in front of the microscope). The five pol objectives mounted on the nose piece are: XXx, XXx, XXx, XXx, and XXx. The upper slider contains a Bertrand lens, to allow telescopic observation of the rear lens element of the objective. The included manual is available as a scanned copy: Directions, DIALUX-POL Research Polarizing Microscope. The catalog scan is from: Braun-Knecht-Heiman-Co. (Division of Van Waters & Rogers, Inc.) Catalog No 63, Laboratory Instruments Apparatus and Supplies. San Francisco. (1961). An earlier catalog describing various Leitz products is also provided: Ernst Leitz. Polarizing Microscopes and Accessories. Wetzler. (1950) available as an illustrated index with individual pages.

Accessories

Ultropac Illuminator with built in lamp in its own fitted case with accessories. (Ernst Leitz GMBH, Wetzlar; HSU Chemistry Dept., 1961).

The illuminator consists of a housing with built-in beam splitting mirror, illuminating attachment and bayonet changing mount for objectives. It furnishes darkfield illumination for opaque specimens, and may be combined with transmitted light from the substage condenser. The custom mahogany case displayed behind it is slotted to slide into special brackets in the Dialux cabinet. An earlier model is described on p39 of the Leitz catalog, Polarizing Microscopes and Accessories, 1950).

Large accessories box which slots into the fitted microscope case

The box is fitted to contain eyepieces, objectives, ten centring changing collars (three have objectives installed in image, bottom), a Berek Compensator, a gypsum plate, a mica plate, a quartz wedge, two periplan "photographic" eyepieces, two stage clips and some miscellaneous items.

A number of the items shown in the photo of the open case are displayed near the microscope, identified by numbers:

1. Whole-wave “gypsum red 1” wave compensator plate.

2. ¼ wave “mica” wave compensator plate.

3. Quartz wedge 4-wavelength wave compensator plate.

6. Standard polarizer (replaced by synchronizing unit).

Number (5) the mechanical stage, is on the microscope holding a slide.

Number (4) the Berek tilting compensator is shown below:

An eyepiece micrometer and a stage micrometer in individual leatherette covered boxes are displayed adjacent to the microscope case.

© R. Paselk 2013, Last modified 3 January 2021