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Abbe condenser acetate add a fragment adjustment ammonium hydroxide amorphous amount angles ANISOTROPIC aperture appear arsenate barium bichromate calcium carbonate cell cesium cesium chloride chloride chromate color compound concentrated copper cover glass cross-hairs Crystal Forms crystalline decant device diameter diaphragm dilute disk dissolved employed evaporate examination eyepiece fibers heating Hexagonal hydrochloric acid instrument iodide ISOTROPIC lamp lens light rays liquid magnesium material means mercuric metal Method micro microchemical micrometer microscope millimeters mirror mixtures monoclinic nicols nitrate nitric acid numerical aperture object slide oblique obtained ocular optic axis Orthorhombic oxalate particles phosphate placed plane plates platinum polarized potassium precipitate preparation present prisms radiant reaction reagent Recrystallize reflected refractive index salts scale screw separate shown in Fig silver Silver Nitrate sodium soluble solution specimen stage strontium substage substance sulphate sulphocyanate sulphuric acid surface test drop Tetragonal thin tiny tion Triclinic tube ultramicroscope usually vertical illuminators yield zinc
Page 5 - This angle is obviously that of the cone of light rays whose apex lies in the optic axis of the microscope at the point where the axis passes through the plane of the object and the diameter of whose base is equivalent to the opening of the front lens combination of the objective. Dry objectives may be compared with each other with reference to their angular aperture. In general the angular aperture depends largely upon the diameter of the front combination of the objective, and usually in objectives...
Page 172 - Elasticity." l In the orthorhombic system the axes of elasticity coincide with the crystallographic axes. In the monoclinic, one axis of elasticity coincides with the b-axis, the other two axes of elasticity are in a plane of symmetry at right angles to b, but are coincident with neither the c-axis nor the a-axis. In the triclinic system no axis of elasticity is parallel with a crystallographic axis. For the relations between axes of elasticity and refractive index, see Chapter IX, page 194. Observations...
Page 311 - Cd(CNS)2-Hg(CNS)2 in brilliant colorless, probably orthorhombic prisms, usually several times as long as broad but the appearance of these prisms varies with the conditions which obtain at the time of their formation, as, for example, the concentration, depth of the test drop, amount of reagent added, acidity, etc. These variations are, however, not of a kind to render the test doubtful, long prisms, either singly or in groups being the rule. Even a small amount of cadmium destroys the feathery and...
Page 340 - ... of hexagonal plates. Their color by transmitted light varies from a reddish yellow in very thin plates to reddish brown with a tinge of dirty violet or even deep black as the thickness of the crystal increases. Remarks. — The arsenic acid can be added directly to the test drop to either neutral or to weak nitric acid solutions, but the best and most uniform results seem to follow the procedure suggested above. The amount of ammonium hydroxide added to the reagent drop must never be sufficient...
Page 339 - Finally many of the crystals which separate have the appearance of hexagonal plates. Their color by transmitted light varies from a reddish yellow in very thin plates to reddish brown with a tinge of dirty violet or even deep black as the thickness of the crystals increases.
Page 328 - Recrystallized in the presence of Group I, double chlorides result, which generally separate more slowly. The crystal form is quite different from that of the normal salt. It is quite important that the student should be familiar with at least the double chloride of cesium and lead (cesium chloroplumbate), since this compound not infrequently makes its appearance when testing for tin with cesium chloride and is quite apt to puzzle the beginner. Alkalies convert lead chloride into a basic chloride...
Page 297 - The crystals of strontium oxalate are similar to those obtained with calcium, but are usually distinctly larger, and crosses, prisms, and four-pointed rosettes are more abundant and larger. The crystals are either tetragonal or monoclinic depending upon whether formed in the cold or separating from hot solutions. Precautions. To avoid error when testing with oxalic acid, it is always advisable, after the crystals have well formed, to draw off the supernatant solution and add dilute sulphuric acid...
Page 333 - ... thrown down as an amorphous mass. If the precipitate is wholly crystalline, either silver is absent or else present in very small amount. In order to identify silver in an amorphous precipitate it is necessary to recrystallize it. Before so doing it is always advisable, and often necessary, to first remove the solution from the precipitate and wash the latter. If the hydrochloric acid has been carefully added and the drop not stirred, it is easy to draw off the clear solution from the curdy,...
Page 345 - Of the above listed alum-forming elements, aluminum is the only one which unites with cesium or rubidium sulphates to form easily crystallizable alums. The other elements unite with these two sulphates only with difficulty, and the alums formed can be regarded, from a microchemical standpoint, as difficultly crystallizable. Sodium, potassium and ammonium sulphates readily unite to form more or less crystallizable alums with the other alum-forming elements as well as with aluminum.
Page 329 - Thallous salts yield with hydrochloric acid star- and cross-like crystallites differing considerably from those given by lead. There is little danger of confusing these two elements, since recrystallizing thallous chloride from hot water, in which it, like lead chloride, is soluble, yields well-formed cubes. In the presence of chlorides of antimony and bismuth complex chlorides of low solubility are sometimes formed, against which the analyst should be on his guard. Silver gives an amorphous precipitate...