Cobalt masking

The procedure utilises eriochrome blue black RC (also called pontachrome blue black R Colour Index No. 15705) at a pH of 4,8 in a buffer solution. Beryllium gives no fluorescence and does not interfere iron, chromium, copper, nickel, and cobalt mask the fluorescence fluoride must be removed if present. The method may be adapted for the determination of aluminium in steel. 

The ACGIH adopted TLV/TWA for 1992—1993 for fluorides as F is TWA 2.5 mg/m, and for cobalt as Co metal dust TWA 0.05 mg/m. Dust masks should be used while handling both the cobalt fluorides and all other cobalt compounds. CoF is shipped as an oxidizer and a corrosive material. 

Inhalation of extremely fine carbide, cobalt, and nickel powders should be avoided. Efficient exhaust devices, dust filters, and protective masks are essential when handling these powders. 

Sometimes the metal may be transformed into a different oxidation state thus copper(II) may be reduced in acid solution by hydroxylamine or ascorbic acid. After rendering ammoniacal, nickel or cobalt can be titrated using, for example, murexide as indicator without interference from the copper, which is now present as Cu(I). Iron(III) can often be similarly masked by reduction with ascorbic acid. 

In the back-titration small amounts of copper and zinc and trace amounts of manganese are quantitatively displaced from the EDTA and are complexed by the triethanolamine small quantities of cobalt are converted into a triethanolamine complex during the titration. Relatively high concentrations of copper can be masked in the alkaline medium by the addition of thioglycollic acid until colourless. Manganese, if present in quantities of more than 1 mg, may be oxidised by air and forms a manganese(III)-triethanolamine complex, which is intensely green in colour this does not occur if a little hydroxylammonium chloride solution is added. 

MOSFETT s, and silicon oxide is deposited. The source/drain positions where electrical contact is to be made to the MOSFETs are defined, using the oxide-removal mask and an etch process. For shallow trench isolation, anisotropic silicon etch, thermal oxidation, oxide fill and chemical mechanical leveling are the processes employed. For shallow source/drains formation, ion implantation techniques are still be used. For raised source/drains (as shown in the above diagram) cobalt silicide is being used instead of Ti/TLN silicides. Cobalt metal is deposited and reacted by a rapid thermal treatment to form the silicide. Capacitors were made in 1997 from various oxides and nitrides. The use of tantalmn pentoxide in 1999 has proven superior. Platinum is used as the plate material. 

Several ions (e.g., manganese, iron (II), iron (III), cobalt, nickel, copper, zinc, cadmium, lead, and uranyl) react with pyrocatechol violet, and to some extent are extracted together with aluminium. The interferences from these ions and other metal ions generally present in seawater could be eliminated by extraction with diethyldithiocarbamate as masking agent. With this agent most of the metal ions except aluminium were extracted into chloroform, and other metal ions did not react in the amounts commonly found in seawater. Levels of aluminium between 6 and 6.3 pg/1 were found in Pacific Ocean and Japan Sea samples by this method. 

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. 

Cobalt chloride (CoClj) is used to manufacture vitamin even though the compound itself can cause damage to red blood cells. It is also used as a dye mordant (to fix the dye to the textile so that it will not run). It is also of use in manufacturing solid lubricants, as an additive to fertihzers, as a chemical reagent in laboratories, and as an absorbent in gas masks, electroplating, and the manufacture of vitamin B. ... 

A secondary, more subtle, effect that can be utilized in the achievement of selectivity in cation exchange is the selective complexation of certain metal ions with anionic ligands. This reduces the net positive charge of those ions and decreases their extraction by the resin. In certain instances, where stable anionic complexes form, extraction is suppressed completely. This technique has been utilized in the separation of cobalt and nickel from iron, by masking of the iron as a neutral or anionic complex with citrate350 or tartrate.351 Similarly, a high chloride concentration would complex the cobalt and the iron as anionic complexes and allow nickel, which does not form anionic chloro complexes, to be extracted selectively by a cation-exchange resin. 

Colorimetric Methods have frequently been suggested,1 but of these, that originated by Skey and studied by several others 2 appears to be the most useful. It hinges on the fact that potassium thiocyanate yields a blue colour with solutions of cobalt salts, due to the formation of cobalt thiocyanate. On adding alcohol and ether to the liquid, a blue layer is produced. This is destroyed by mercuric chloride, sodium acetate, or sodium thiosulphate, and is masked by the presence of iron salts in consequence of the intense red colour of ferric thiocyanate consequently these substances should not be present when the colorimetric test is applied. 

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. 

II. Dry tests (blowpipe test) Aluminium compounds when heated with sodium carbonate upon charcoal in the blowpipe flame give a white infusible solid, which glows when hot. If the residue be moistened with one or two drops of cobalt nitrate solution and again heated, a blue infusible mass (Thenard s blue, or cobalt meta-aluminate) is obtained. It is important not to use excess cobalt nitrate solution since this yields black cobalt oxide Co304 upon ignition, which masks the colour of the Thenard s blue. 

The sodium flame masks that of other elements, e.g, that of potassium. Mixtures can be readily detected with the direct vision spectroscope (see Fig. II.4). A less delicate method is to view the flame through two thicknesses of cobalt blue glass, whereby the yellow colour due to sodium is masked or absorbed, and the other colours are modified as listed in Table V.3. 

Antimony, zinc, and aluminium salts do not interfere aluminium should, however, be kept in solution by the addition of sufficient sodium hydroxide the influence of copper, nickel, and cobalt salts can be eliminated by the addition of potassium cyanide solution iron salts are masked by the addition of a tartrate but if aluminium salts are also present a red colour is produced. Magnesium salts give a similar blue colour, but beryllium can be detected in the presence of this element by utilizing the fact that in ammoniacal solution the magnesium colour alone is completely destroyed by bromine water. 

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. 

The color and constitution of object 7 are similar to those of the violet trailing stick, object 5. The color is caused by iron in the presence of manganese and cobalt. There is half as much copper (0.16%) in this object as in object 5 (0.34%), so that copper at this level must not influence coloring, or its effect is masked by the higher proportion of iron. 

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