This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1912 edition. Excerpt: ...give regularly bounded figures. Staining Methods.--The staining methods, which play so important a role in organic microscopy, are only used occasionally in the investigation of thin sections because only a few minerals in their natural condition would absorb the stains and those that do are principally thick, ...
Read More
This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1912 edition. Excerpt: ...give regularly bounded figures. Staining Methods.--The staining methods, which play so important a role in organic microscopy, are only used occasionally in the investigation of thin sections because only a few minerals in their natural condition would absorb the stains and those that do are principally thick, scaly to fibrous aggregates of good cleavable minerals, but even they can scarcely be differentiated or recognized in this way. Usually, before a mineral in a thin section is stained, it is treated on the object glass with dilute acid until it has been so altered that it is covered with a gelatinous precipitate. This gelatinous material absorbs the stain evenly and retains it so that it cannot be washed out. After the etching action, which is always only superficial, the acid must be thoroughly washed away before the stain is applied or it may be destroyed. The section is placed in an evaporating dish filled with distilled water to which a few drops of a solution of Congo red or malachite green or any other permanent dye have been added. If it is left to stand for several hours, the dye is absorbed quite evenly by the gelatinous precipitate. It is then thoroughly washed in running water, dried, and covered again with Canada balsam. Certain silicates dissolve in hydrochloric acid and the silica separates in a gelatinous condition, covering the thin section. A thin film of dilute hydrochloric acid is put on the mineral in the thin section so that the etching will take place only on the surface and the whole mineral will not be dissolved. This reaction is characteristic for nepheline, which is otherwise often very difficult to recognize in the ground mass of a basaltic rock. But plagioclase and scapolite rich in lime, sodalite, melilite, ..
Read Less
