Show qualitative tests for the rarer metals BY ROY FRANKLIN HEATH I 1 the outlines below afford quick and ac curate means for the qualitative determination tion of some of the rarer minerals and fores res which are so important at this time the directions are simple with no reference to chemical reactions they are intended for the prospector who desires simple and reliable tests molybdenum occurrence the sulphide usually in crystalline rocks in the form of bluish gray scales of fine granular masses 1 resembles graphite the oxide P yellowish white to light yellow with dull to silky luster lead molybdenum color varies from yellow to red often brown to green ores of molybdenum occur ast socia ted with lead ores but are also found i in disseminated deposits of copper silver and zinc ores place five grams of the powdered sample in a casserole or small porcelain crucible add fifteen cc concentrated sulphuric acid and evaporate slowly to dryness cool and if molybdenum is present a characteristic blue coating will be formed which is the mixture of the oxides with finely divided molybdenum another test as to add to about five grams of the finely powdered substance in a small beaker or flask twenty cc of concentrated cent rated hydrochloric acid the solution will turn green or of greenish coloration after it has been boiled a short time dilute with thirty cc water add strip of me callic tin warm slightly to start reaction solution becomes blue and later brown the blue color may be of short duration due to rapid reduction whence the solution may turn brown without visible notice of the blue reaction nickel t occurrence the silicate found with in oregon color dark green to greenish white sometimes unctuous and if friable will cause stain usually in compact masses capillary pyrites is the sulphide occurs with iron ores brass colored specimens in the form forin of long spear like crystals have been found in cascade county montana copper nickel is of uncertain composition carries also cobalt antimony and arsenic brittle mineral of pale copper red which soon tarnishes the sulphide of nickel and iron color light bronze yellow often with or magnetic pyrites also carries nickel and cobalt v metallurgical chemist billings Alon montana tana references chemistry fresenius colin cohn vanadium page 10 all R of U S 1909 tungsten page M R of U S 1908 molybdenum page aa M R of U S fios 1908 to five grams of the finely powdered mineral add five cc nitric and fifteen cc hydrochloric acid doil boil until decomposed the solution will be of greenish color if nickel is present in a large quantity As a further test divide the solution into four portions and make se test with each part as follows part I 1 add a few drops of potassium cyanide solution to solution suspected of containing nickel A green precipitate indicates nickel the precipitate is soluble in excess of potassium cyanide solution copper interferes with this test part II if add five to ten cc solution of sodium hydroxide A light green precipitate is produced if nickel is present the precipitate is insoluble in excess of the reagent but is soluble in a solution of ammonium chloride cobalt coba it if nickel is present chances are cobalt is present also test for it with the remaining two parts as follows part III dilute solution with water to double volume add fifteen cc strong acetic acid add slowly a weak solution of potassium nitrite A light lemon yellow prep civitate is formed which settles out on standing this can be further confirmed com firmed as a salt of cobalt by making a borax bead collecting a small quantity of this precipitate on the bead and heating in the flame cool the characteristic deep blue color is imparted to the bead if cobalt is present part IV dring bring solution suspected of cobalt and nickel to near boiling add ammonium sulphide solution clear until precipitation is complete filter and collect residue wash once with hydrogen sulphide water then a cold dilute solution of hydrochloric acid A black precipitate remaining indicates cobalt and nickel test cobalt by bead test by collecting a small amount of the residue heating and cooling if cobalt is absent and nickel present the bead is yellowish brown cobalt is always associated more or less with nickel ores in proceeding to test for cobalt decompose sample as given for nickel and apply tests given in parts III and IV the most important ores of cobalt are or cobalt glance a silver white to gray brittle mineral Linna elte or cobalt pyrites steel gray in color brittle having metallic luster and an ore of variable composition but always containing nickel with other common metals it is steel white to gray and brittle tin occurrence stream tin or tin stone the oxide found in veins with granite quartz and scheelite in I 1 lower ower oxidized and sulphide ore bodies also in placer deposits with gold etc hard and heavy color brown black red gray and yellowish occurs as brilliant crystals dull rounded masses and pebbles tin pyrites the sulphide composition uncertain found in many copper deposits color steel gray to black to five to ten grams of the fine ore add five cc nitric and fifteen cc of hydrochloric acid heat until decomposed add drop by drop a dilute solution of gold chloride if tin is present a bluish green coloration is produced which slowly changes to a brownish color add a small lump of the suspected sample about five grams to a dilute solution of nitric acid in a test tube heat to bolling boiling immerse zinc strip in solution metallic tin is deposited after some time the nitric acid solution should be of greenish color after being boiled when tin is present titanium the oxide found associated with hematite magnetite feldspar etc color red reddish brown to black widely distributed tri buted but ores of commercial in are scarce powder fine mesh five to ten grams of the material add ten cc concentrated hydrochloric acid boil for five minutes add two to five grams tin or zinc tin preferred because of slow action to the solution after it has been diluted with cc water bring to boll boil if titanium is present it will give a violator vio violet letor or light blue color which if reaction is allowed to proceed forms blue precipitate which later turns dirty white tungsten occurrence scheelite lime tungsten color white yellowish brownish reddish to green manganese tungsten dark grayish black the of manganese and iron brown to brown black and iron tungsten color black to reddish powder finely ten grams grains of the sample mix with twenty five grams of potassium or sodium carbonate heat until fusion is completed or if it is impossible to secure sufficient heat for fusion heat until the mixture is caked cool the mass remove contents to a beaker or flask add twenty five cc concentrated acid and twenty five cc of water bring to boll boil and evaporate excess of water divide into two portions to part I 1 add three to five grams grains of zinc if tungsten is present the solution will turn first blue then wine colored and finally brown if action is too gorious vi the blue coloration is invisible in which case the first color noticed is the wine red to part II if add three to four grams of tin heat if necessary to start action if tungsten is present the solution will turn blue purple wine red and slowly to brown vanadium occurrence occurs in masses of bright red yellow or brown crystals associated socia ted with lead zinc and often low grade complex ores color black brown to olive green found associated with and ro place five to eight grams of the fine powdered sample in a small flask add ten cc nitric acid and a like quantity of hydrochloric acid bring to boll boil and boil for five minutes add ten cc sulphuric acid and bring to boil dilute to cc with water filter off insoluble matter add to the clear filtrate drop by drop hydrogen peroxide solution A brownish red precipitate indicates vanadium the test can be carried further by adding three to five grams of metallic zinc the solution will turn a fine blue uranium occurrence pitchblende associated socia ted in both grani tic rocks and metallic veins often with other metallic ores it is a black brownish massive mineral of pitch like appearance there are several varieties grind finely five to ten grams of the material add ten cc nitric acid and twenty cc hydrochloric boil and digest until decomposed evaporate to dryness take up in water boil and filter divide filtrate into three portions to part I 1 add slowly three to five cc of sodium hydroxide solution the presence of uranium is shown by a light yellow precipitate to part II 11 add drop by drop a weak solution of potassium ro the presence of uranium is shown by a reddish brown precipitate or coloration to part III add five cc hydrochloric acid and three to four grams metallic zinc warm slightly a green color is produced due to reduction from to uranous compounds thorium occurrence monazite in the form 01 small brown resinous crystals or as yellow translucent grains in sand or angile or the silicate in black and yellow crystals translucent to transparent with resinous luster powder a small quantity of the sample add ten to twenty cc concentrated s sulphuric ul acid boil dilute filter divide citrate into three portions to part I 1 add drop by drop a solution of sodium hydroxide the presence of thorium is shown by a white precipitate insoluble in excess of the reagent but soluble in nitric sulphuric and hydrochloric acids to part II 11 add drop by drop a solution of ammonium carbonate a white precipitate forms if thorium is present which is soluble in excess of the reagent to part III add a few crystals of oxalic acid a white precipitate soluble in acetic acid denotes presence of thorium |