134 The substance, which is an arsenide or sulpharsenide, 135 136 Not wholly volatilized, or exhibiting no sulphur-reaction, The substance is red....... 137. ...Orpiment. The substance is very volatile..................................... Arsenous Acid. 102 136 137 102 SELENIUM COMPOUNDS. Metallic aspect... .... Selenide. 138 Not: selenite or selenate; the substance is well calcined, and the metal detected, beginning with No.... 102 TUNGSTATES. 139 With Sd on platinum wire in OF1 affords a greenish blue mass.... Not. ..... Wolfram. 140 Heated with Sd in a closed glass tube, evolves am The analogy in chemical composition and properties, For the discrimination of the native silicates, v. Chapter VI, 102 SIXTH CHAPTER. ON THE DISCRIMINATION OF MINERALS BY MEANS OF THE BLOWPIPE, AIDED BY HUMID ANALYSIS. By the methods given in the preceding chapters, we can readily detect the constituents of most inorganic compounds, whether prepared artificially or occurring in nature; especially if heavy metals form the principal constituents. But these methods do not enable us to discriminate the different native silicates, and other mineral bodies, which consist essentially of such substances that do not show any very characteristic reactions before the blow-pipe, as ex. gr. the alkaline earths. In some cases we may succeed in ascertaining the principal ingredients of the substance under examination, but fail in establishing the mineral species. To attain this end more securely, we must pursue a course, composed of an examination of the physical properties of the body and of blow-pipe operations, aided by humid analysis. The course adopted in this “Manual" is that given by Franz von Kobell, as laid down in his "Tafeln zur Bestimmung der Mineralien." The following is only an extract, slightly modified, from this treatise: The minerals, according to Von Kobell's system, are arranged in two large groups, the first embracing those possessing metallic lustre, the second those devoid of metallic lustre. To avoid mistakes, originating in the fact that some minerals occur sometimes with, and sometimes without, metallic lustre, these minerals will be found enumerated in both groups. The same precaution has been taken in regard to those species in which degree of fusibility, whether below or above 5, might appear doubtful. The degree of fusibility is to be judged of from the following scale : 1. Gray Antimony.-Fusible in coarse splinters in the flame of a candle. 2. Natrolite.-Fusible in fine splinters in the flame of a candle. 3. Almandine or Iron-Garnet.-Easily fusible before the blow pipe. 4. Actinolite (a variety of hornblende).-Fusible before the Blp in coarse splinters. 5. Orthoclase.-Fusible before the Blp in fine splinters. 6. Broncite.-Fusible on the edges in very fine splinters. The fusibility, when equal to that of actinolite, is designated by 4; when between that of natrolite and almandine, by 2, 5, and so on. The two large groups are divided into classes according to the fusibility; these again in divisions, &c., by which means we obtain the following general classification: GROUP I. MINERALS POSSESSING A METALLIC LUSTRE. CLASS I. Native malleable metals, and mercury. CLASS II. Fusibility 1-5, or readily volatile. Division 1. Give a strong arsenical odor on Ch, Division 2. Give on Ch, or in an open tube, the horse-radish odor of selenium. Division 3. Give in an open tube a white or grayish sublimate, which is fusible into colorless drops, indicative of tellurium. Division 4. Give antimonial fumes on Ch. Division 5. Give with Sd on Ch a sulphur-reaction, but do not give indications as above. Division 6. Do not exhibit the properties of the preceding di visions. CLASS III. Infusible, or fusibility above 5, and not volatile. Division 1. Give with Bx, in small quantities, the manganese reaction, Division 2. Treated on Ch in RF1, become magnetic. Division 3. Resembling those of division 2. GROUP II. MINERALS NOT POSSESSING METALLIC LUSTRE. CLASS I. Easily volatile, or combustible. CLASS II. Fusibility 1-5, not, or only partially, volatile. Part I. Give with Sd on Ch a metallic globule or magnetic metallic mass. Division 1. Give with Sd a globule of silver. Division 3. When moistened with hydrochloric acid, color the flame blue, and give with nitric acid a solution which, on addition of an excess of ammonia, assumes an azure-blue color. Section 1. Give on Ch a strong arsenical odor. Section 2. Give no arsenical odor. Division 4. Impart to the Bx bead a blue color. Division 5. When fused on Ch in RFI, give a black or gray metallic magnetic mass. Section 1. Give on fusion a strong arsenical odor. Section 2. Soluble in hydrochloric acid without leaving a perceptible residue, and without gelatinizing. Section 3. With hydrochloric acid, form a jelly, or are decomposed with separation of silica. Section 4. But little affected by acids. Division 6. Not belonging to either of the preceding divisions. Part II. With Sd on Ch, give no metallic globule, or magnetic metallic mass. Division 1. After fusion and continued heating on Ch or in the forceps, have an alkaline reaction, and change to blue the color of a moistened red litmus-paper. Section 1. Easily and completely soluble in water. Section 2. Insoluble in water, or soluble with difficulty. Division 2. Soluble in hydrochloric acid without leaving a perceptible residue, some also soluble in water; not gelatinizing. Division 3. Soluble in hydrochloric acid, forming a perfect jelly. Section 1. Giving water in a matrass. Section 2. Giving traces, or no water in a matrass. Division 4. Soluble in hydrochloric acid with separation of silica, without forming a perfect jelly. Section 1. Giving water in a matrass. Section 2. Giving traces, or no water in a matrass. Division 5. Little affected by hydrochloric acid; imparting to the Bx bead the color of manganese. Division 6. Not belonging to either of the preceding divisions. CLASS III. Infusible, or fusibility above 5. Division 1. After ignition moistened with SoCo and again ignited, assume a bright-blue color. Section 1. Giving much water in a matrass. Section 2. Giving little or no water in a matrass. Division 2. Moistened with SoCo and ignited, assume a green color. Division 3, After ignition have an alkaline reaction, and turn into blue the color of a moistened red litmus-paper. Division 4. Completely soluble, or nearly so, in hydrochloric or nitric acid, without gelatinizing or leaving a perceptible residue of silica. Division 5. With hydrochloric acid, form a jelly or are decomposed with separation of silica. Section 1. Giving water in a matrass. Section 2. Giving traces, or no water in a matrass. Division 6. Not belonging to either of the preceding divisions. Section 1. Hardness below 7. Section 2. Hardness=7, or above. GROUP I. MINERALS POSSESSING A METALLIC LUSTRE. CLASS I. NATIVE MALLEABLE METALS, AND MERCURY. Native silver, see § 197. Native Gold and Electrum (alloy of silver and gold), see § 150. Native copper, see § 134. Native Lead, characterized by coating on charcoal (see § 23) and softness; H=1.5. Native Platinum, see § 152. Native Palladium, distinguished from the preceding Native Mercury, see § 187. CLASS II. FUSIBILITY 1 TO 5, OR READILY VOLATILE. |