Cobalt glass

Cobalt ores are often found in association with copper(II) sulfide. Cobalt is a silver-gray metal and is used mainly for alloying with iron. Alnico steel, an alloy of iron, nickel, cobalt, and aluminum, is used to make permanent magnets such as those in loudspeakers. Cobalt steels are hard enough to be used as surgical steels, drill bits, and lathe tools. The color of cobalt glass is due to a blue pigment that forms when cobalt(II) oxide is heated with silica and alumina. 

Carmine Lithium compounds (masked by barium or sodium), are invisible when viewed through green glass, appear violet through cobalt glass. 

Scarlet Calcium compounds (masked by barium), appear greenish when viewed through cobalt glass and green through green glass. 

VIOLET Potassium compounds other than silicates, phosphates and borates rubidium and cesium are similar. Color is masked by lithium and/or sodium, appears purple-red through cobalt glass and bluish-green glass. 

YELLOW Sodium, even the smallest amount, invisible when viewed through cobalt glass. 

Cobalt glass, color, 7 331 CobaltCII) hexaaquo ion, 7 229 Cobalt hexahydrate, analysis, 7 237t Cobalt high temperature alloys, 7 223-224 Cobalt hydroxide, analysis, 7 237t Cobalt(II) hydroxide, 7 230 uses, 7 240t... 

Potassium. — The yellow color imparted by sodium bicarbonate to the flame, when observed through cobalt glass, should have at most a transient violet tinge. 

Little sampling was performed with the cobalt glass since a limited supply of chips was available. The sampling did, however, confirm uniformity. The techniques of measurement are quite straightforward but require some refinements over the cellophane. The orientation of the chips appears to be quite critical. 

A table showing the colours imparted to the flame by salts of different metals is given in Section V.2(3). Carry out flame tests with the chlorides of sodium, potassium, calcium, strontium, and barium and record the colours you observe. Repeat the test with a mixture of sodium and potassium chlorides. The yellow colouration due to the sodium masks that of the potassium. View the flame through two thicknesses of cobalt glass the yellow sodium colour is absorbed and the potassium flame appears crimson. 

Table V.3 Flame test with cobalt glass...

Flame colouration Flame colouration through cobalt glass Inferences... 

Confirm by flame test and view through two thicknesses of cobalt glass red colouration (usually transient). 

It is advisable to test the cobalt glass with a potassium salt to be certain that the glass is satisfactory some samples of cobalt glass completely absorb the red lines from potassium. It is recommended that a hand spectroscope be used, if available. 

Dry test Flame colouration. Lithium compounds impart a carmine-red colour to the non-luminous Bunsen flame. The colour is masked by the presence of considerable amounts of sodium salts, but becomes visible when observed through two thicknesses of cobalt glass. 

Figure 7 Ar matrix of Cr(CO)g doped with H2. Solid lines represent spectrum after broad band irradiation followed by irradiation through cobalt glass. Dashed bnes represent the spectrum of the same matrix after 90 min irradiation with the visible light from a Nemst glower. Band assignments 1, Cr(CO)5(H2) 11, Cr(CO)4(H2)2 III, Cr(CO)4(H2) 6, Cr(CO)6 5, CrjCOjs. (Reprinted with permission from Ref. 99. 1985 American Chemical Society)...

Compounds of sodium are readily identified by the yellow color that they give to a flame. Lithium causes a carmine coloration of the flame, and potassium, rubidium, and cesium cause a violet coloration. These elements may be tested for in the presence of sodium by use of a blue filter, of cobalt glass. 

Properties of cobalt. Ores—smaltite, cobaltite. Alnico and other alloys, Cobaltous chloride, cobaltous oxide, cobaltic hydroxide, potassium cobaltinitrite, potassium cobalticyanide. Cobalt glass. 

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