HexaNitritocobaltate , sodium

Analysis. K or a K compound in the flame gives a reddish-violet (lilac) color. This is due to its emission of404.4,404.7, 766.5, and 769.9 nm photons. These photon lines allow for the determination of K by AA (limit of detection = 20 ppb), ETAAS (1 ppb), and ICPAES (0.1 ppb). This latter limit is also attainable by ICPMS and IC. Spots tests with sodium hexanitritocobaltate(III) and dipicrylamine both detect 100 ppm of K. 

Sodium hexanitritocobaltate(III) solution Nai Co(N02)6 yellow precipitate of potassium hexanitritocobaltate(III) ... 

Place a drop of the neutral or acetic acid test solution on a black spot plate, and add a drop of 01m silver nitrate solution and a small amount of finely powdered sodium hexanitritocobaltate(III). A yellow precipitate or turbidity appears. 

Chloroplatinic acid, tartaric acid or sodium hexanitritocobaltate( III) solution no precipitate with solutions of sodium salts. 

Sodium hexanitritocobaltate (III) solution light-red precipitate of thallium(I) hexanitritocobaltate(III), Tl3 [Co(N02)6]. 

Tartaric acid, sodium hexanitritocobaltate(III) or hexachloroplatinic acid solution no precipitate (distinction from potassium). A precipitate of lithium hexanitritocobaltate(III) is, however, produced in very concentrated (almost saturated) solutions of lithium salts interference with the sodium hexanitrito-cobaltate(III) test for K+ is therefore unlikely. 

The amine (0.1 mole) is diazotized in hydrochloric or sulfuric acid solution by sodium nitrite (7 g), the volume of solution being kept as small as possible. The diazonium salt solution is neutralized with calcium carbonate and filtered, and trisodium hexanitritocobaltate (15 g) is stirred into the filtrate, whereupon the trisdiazonium salt usually separates as a solid. For conversion into the nitro compound this salt (10 g), finely powdered, is added in portions, at room temparature, with good stirring, to a solution of sodium nitrite (lOg) and copper sulfate (10 g) in water (60 ml) in which copper(i) oxide (4 g) is suspended. When evolution of nitrogen ceases the nitro compound is isolated either by extraction with a solvent, e.g., chloroform, or by basification of the solution and steam-distillation.172... 

Sodium hexanitritocobaltate(III), (Na-i[Co(N02)(,J) yellow precipitate of ammonium hexanitritocobaltate(III), (NH4)3[Co(N02)6], similar to that produced by potassium ions ... 

Sodium hexanitritocobaltate(III) (0.167m). Dissolve 6.73g sodium hexanitrito-cobaltate(III) (sodium cobaltinitrite) in 100 ml water. 

In the last step of the analysis, 1 ml of a freshly prepared 100 g/1 solution of sodium cobaltnitrite R is added to the mixture in test tube B, upon which a yellow precipitate of ammonium hexanitritocobaltate(III) is formed. 

If sodium is more abimdant, a mixed complex is formed with the composition K2Na[Co(N02)6]- The two complexes are alike in appearance. This reaction was used in the classical inorganic analysis to isolate potassium from the other alkali metals. The precipitate was isolated and washed and a determination was then performed colorimetrically on the cobalt ion. In many cases the silver, zinc, or lead salt of hexanitritocobaltate was used as a reagent. 

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