Cobalt blue chloride

Cobalt II) halides can be obtained by direct combination of the elements, or by dehydration of their hydrates. Anhydrous cobalt(II) chloride is blue, and the solid contains octahedrally-coordinated cobalt the hydrated salt C0CI2. bHjO is pink, with each cobalt surrounded by four water molecules and two chloride ions in a distorted octahedron. 

These are of two general kinds octahedral, pink complexes and tetrahedral, blue complexes. If cobalt(II) chloride is dissolved in aqueous solution, the predominant species is the hexaaquo-ion [ColHjO) ] (pink). If this solution is heated, it becomes blue, and the same effect is observed if chloride ion is added in excess. This colour change is associated with the change... 

When cobalt(II) chloride was dissolved in water, a pink solution A was formed. The addition of concentrated hydrochloric acid to A gave a blue solution B. If solution A was treated with concentrated ammonia solution a blue-green precipitate was formed upon addition of further ammonia solution followed by the passage of air through the mixture, an orange-red solution C was produced. 

Colour - A striking feature of transition-metal compounds is their colour. Whether it is the pale blue or pink hues of copper(ii) sulfate and cobalt(ii) chloride, or the intense purple of potassium permanganate, these colours tend to be associated most commonly with transition-metal compounds. It is rare for compounds of main group metals to be highly coloured. 

Crystallization yields the commercial product, pink heptahydrate. Further oxidation of this salt in dilute H2SO4 with ozone or fluorine produces hydrated cobalt(III) sulfate, 002(804)3 I8H2O. This blue octadecahydrate, 002(804)3 I8H2O also is obtained by electrolytic oxidation of cobalt(II) chloride or any cobalt(II) salt solution in 8M sulfuric acid. 

Phosphates, Cobalt (II) chloride (1% in acetone or Blue spots upon wanning the plate at 90... 

Cobalt (II) thiocyanate An ammonium thiocyanate (15%)/cobalt (II) chloride (5%) solution in water is sprayed on the plate, yielding blue spots. 

Ten grams of cobalt(II) chloride hexahydrate is dissolved in 100 ml. of water at 0°C., and 50 ml. of 15 M (0.880 sp. gr.) ammonia at 0°C. is added. A brisk stream of oxygen (or air) is sucked through the resultant cooled solution as described in Sec. A, in this case for 45 minutes (or 2 hours if air is used). The solution is kept at 0°C. while ammonium peroxodisulfate (6 g.) dissolved in a minimum amount of ice-cold water is added, and the solution is allowed to stand for up to 10 minutes. Ice-cold concentrated hydrochloric acid is slowly added with stirring (the temperature being kept very close to 0°C.) until the solution is acidic, as indicated by pH papers (30-40 ml. of acid is required). The solution is kept ice-cold until precipitation of the product is complete. The blue-green solid is filtered off and washed with ethanol and then with diethyl ether. 

Both the 1,4-azaphosphorinane 24 free base and its hydrochloride form 1 1 blue complexes with cobalt(II) chloride, which gave highly conductive solutions in absolute ethanol. The 31P-NMR peak is at —22.2 ppm, which is typical for a quaternary phosphorus atom (73IC243). 

Cobalt Oxy-chloride is obtained as a blue precipitate turning red on pouring a hot solution of cobalt chloride into dilute ammonium hydroxide. The formula CoCl2.3Co0.3-5H20, has been attributed to it.1 Another basic salt, CoC.]2.Co(OH)2.5H20, is stated to result as a precipitate by the action of calcium carbonate upon aqueous solutions of cobalt chloride.2... 

Linn10] is added to 3.57 g. (0.015 mole) cobalt(II) chloride hexahydrate in 15 ml. of methanol. Acetone (15 ml) is added, and the solution is allowed to stand overnight in a refrigerator. The crystals are filtered by suction, washed several times with acetone, and then dried in vacuo. The cobalt(II) chloride compound decomposes between 285 and 286°. The yield of blue crystals is 3.0 g. (47%). 

The chloride complex is made by adding 4.89 g. (0.03 mole) of 4-methylquinoline iV-oxide [obtained by hydrogen peroxide oxidation of 4-methylquinoline (lepidine) (Pierce Chemical Company) by the method of Ochiai11] to a solution of 3.57 g. (0.015 mole) cobalt(II) chloride hexahydrate dissolved in 12 ml. of absolute ethanol. This solution is stirred and then evaporated at a mild temperature on a hot plate. The residue is recrystallized from absolute ethanol, filtered by suction, washed several times with cold ethanol, and then dried in vacuo. Dark blue crystals are obtained which melt between 220 and 222°. Yield is 5.54 g. (84%). Then add 4.8 g. (0.032 mole) of silver nitrite to 2.77 g. (0.008 mole) of Co(4-methylquinoline IV-oxide)2-Cl2 in 800 ml. of dry acetone. The solution is treated as in Procedure 1 on page 204. Brown crystals are obtained from a reddish-brown solution. Yield is 1.15 g. (42%). Anal. Calcd. for C20Hi8CoN4O6 C, 51.18 H, 3.86 N, 11.94. Found C, 50.82 H, 3.94 N, 11.22. 

Dry test (flame colouration) Potassium compounds, preferably the chloride, colour the non-luminous Bunsen flame violet (lilac). The yellow flame produced by small quantities of sodium obscures the violet colour, but by viewing the flame through two thicknesses of cobalt blue glass, the yellow sodium rays are absorbed and the reddish-violet potassium flame becomes visible. A solution of chrome alum (310 g 1), 3 cm thick, also makes a good filter. 

Blue anhydrous cobalt(ll) chloride and pink hydrated cobalt(ll) chloride. Since the... 

To analyze hydrates, you must drive off the water of hydration. Often this is done hy heating the compound. The substance remaining after heating is anhydrous, or without water. For example, hydrated cobalt(II) chloride is a pink solid that turns a deep blue when the water of hydration is driven off and anhydrous cobalt(II) chloride is produced. See Figure 11-13. 

Cobalt (Co, at. mass 58.93) occurs predominantly in the II oxidation state. In some complexes it is readily oxidizable to Co(III). The hydroxide Co(OH)2 is precipitated at pH 7.5 and is insoluble in excess of NaOH. Cobalt forms ammine, cyanide, tartrate and EDTA complexes. Blue chloride complexes are formed in fairly concentrated chloride solutions. 

Among inorganic complexes, the blue chloride complex [91], green tricarbonato-cobaltate(lll) (formed in the presence of EDTA) [92], and the mixed pyridine-azide complex [93] are used for determination of Co. 

Methods for the determination of cobalt in soils using thiazolylblue tetrazolium bromide [6] and nitrotetrazolium blue chloride [7] were described. The examined samples were subjected to preliminary separation of the analyte with dithizone. The interference from Fe(IIl) could be masked with ascorbic acid [7]. 

Metal cations usually form complexes with inorganic anions much more readily in organic solvents than in water. For example, the pink cobalt(II) cation requires around 4 or 5 M aqueous hydrochloric acid to be converted to a blue cobalt(II) chloride anion. In a predominantly acetone solution, the intensely blue cobalt(ll) is formed in very dilute hydrochloric acid. Thus, the scope of ion-exchange group separations is increased greatly by carrying out separations in a mixture of water and an organic solvent. 

The equilibrium of the following two cobalt complexes shows a change of the structure and of the coordination number. This equilibrium can also be demonstrated as being dependent on temperature. If hydrochloric acid is added to a pink-colored cobalt(II) chloride solution, the solution changes to blue due to the chloro complex (see E9.10). If the solution is diluted again with water, the pink color returns ... 

Transition metals have a particular tendency to form complex ions because they have more than one oxidation state. This property allows them to act effectively as Lewis acids in reactions with many molecules or ions that serve as electron donors, or as Lewis bases. For example, a solution of cobalt(II) chloride is pink because of the presence of the Co(H20)6 ions (Figure 16.8). When HCl is added, the solution turns blue as a result of the formation of the complex ion CoCl4 ... 

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