Microscope Slide

MICROSCOPE SLIDE, a glass plate on which a microscope specimen is mounted. The usual thickness of a microscope slide is 1.0–1.2 mm; dimensions are 76 x 26 mm (the so-called English size). There are also slides of the same width that are shorter (50 x 26 mm), as well as—for special purposes—other larger formats. The surface of the glass must be strictly flat and the thickness completely uniform; it is also highly desirable that the glass be colorless. Slides with air bubbles are completely unacceptable. The thickness of the microscope slide usually has no special significance, but when using ultracondensers for the dark field of view, strict matching of the slide thickness with the focus of the illuminator is necessary, otherwise the full effect of the dark field will not be obtained (in any case, the slide must not be thicker than the focal length of the illuminator). The edges of the glass must be cut evenly, and even better, ground. For special purposes (for the study of microorganisms in a living state, for tissue cultures), microscope slides are used that have a ground depression of round or oval shape in the middle. In some cases, a low glass ring is glued to the middle of the microscope slide, which, upon application of a coverslip, forms a chamber to which electrodes or capillary tubes can be brought, making it possible to study the effect of an electric current on cells or subject them to the action of various gaseous or liquid reagents. When examining specimens with low magnifications or when using long-focus illuminators, thick plates of plate glass of various formats are used as microscope slides. Ordinary illuminators with such slides make it impossible to use the full light power and aperture of a normal condenser, the focal length of which usually does not exceed 1.2–1.5 mm. Commercial microscope slides usually have a contaminated and often greasy surface. For the preparation of specimens, especially blood smears, the surface of the slides must be thoroughly cleaned. This is most simply achieved by washing the slides with soap or treating them with a solution of potassium permanganate (5–15%) with the addition of 10–15% sulfuric acid; after a few hours, the slides are removed, washed with a solution of oxalic acid (3–5%), then with running water, distilled water, and finally with alcohol. After drying, the surface turns out to be so clean that a drop of water spreads freely over the glass surface. For inscriptions, the ends of the slides are sometimes made frosted, but for the most part, specimens are marked by gluing labels or by writing with ink, the recipe for which can be found in technical manuals on microscopic technique. If ready-made microscope slides are not at hand, they can be cut with a diamond from good glass; for this, for example, the glass of photographic plates is suitable.