Cobalt blue solubility

Cobalt salts. Blue soluble in Red insoluble in Red insoluble in... 

Thiophosphates, Detection.—Many of the reactions already described, such as the production of H2S and phosphoric acid when these salts are treated with acids, will serve to detect the thiophosphates. The alkali and ammonium salts are soluble, the others mostly insoluble. Calcium, barium and strontium monotbiophosphates, barium and strontium dithiophosphates and barium trithiophosphate are insoluble, the other alkaline earth salts soluble. Thiophosphate solutions mixed with alkali sulphides give a green colour with ferric chloride. Monothiophosphates give a blue precipitate with cobalt sulphate soluble in excess of the cobalt salt, dithiophosphates a green precipitate soluble in excess of dithiophosphate, and trithiophosphates a brown solution. Several other tests have been described.3... 

Christensen JM and Poulsen OM (1994) Surveillance programme on Danish pottery painters. Biological levels and hecdth effects following exposure to soluble or insoluble cobalt compounds in cobalt blue dyes. Sci Total Environ 150 95-104. 

Cobalt and nickel yield blue soluble products, and for this reason the following test is not directly applicable in their presence. To detect small... 

Ultramarine blue, sometimes known as cobalt blue, is popular as a tinting color. It produces an attractive reddish cast when added to whites. Ultramarine blue has poor opacity, high heat resistance, and good alkali resistance. While it can be added to latex paints, special grades low in water-soluble salts must be used. Ultramarine blue is often added to whites for extra opacity and a bluish cast, which make them look whiter. 

For a cobalt(ll) salt, the precipitation of the blue->pitik cobalt(II) hydroxide by alkali, or precipitation of black cobalt(II) sulphide by hydrogen sulphide provide useful tests the hydroxide is soluble in excess alkali and is oxidised by air to the brown CoO(OH) . 

Phthalocyanine Dyes. In addition to their use as pigments, the phthalocyanines have found widespread appHcation as dyestuffs, eg, direct and reactive dyes, water-soluble dyes with physical or chemical binding, solvent-soluble dyes with physical or chemical binding, a2o reactive dyes, a2o nonreactive dyes, sulfur dyes, and wet dyes. The first phthalocyanine dyes were used in the early 1930s to dye textiles like cotton (qv). The water-soluble forms Hke sodium salts of copper phthalocyanine disulfonic acid. Direct Blue 86 [1330-38-7] (Cl 74180), Direct Blue 87 [1330-39-8] (Cl 74200), Acid Blue 249 [36485-85-5] (Cl 74220), and their derivatives are used to dye natural and synthetic textiles (qv), paper, and leather (qv). The sodium salt of cobalt phthalocyanine, ie. Vat Blue 29 [1328-50-3] (Cl 74140) is mostly appHed to ceUulose fibers (qv). 

Iron, cobalt, and nickel catalyze this reaction. The rate depends on temperature and sodium concentration. At —33.5°C, 0.251 kg sodium is soluble in 1 kg ammonia. Concentrated solutions of sodium in ammonia separate into two Hquid phases when cooled below the consolute temperature of —41.6°C. The compositions of the phases depend on the temperature. At the peak of the conjugate solutions curve, the composition is 4.15 atom % sodium. The density decreases with increasing concentration of sodium. Thus, in the two-phase region the dilute bottom phase, low in sodium concentration, has a deep-blue color the light top phase, high in sodium concentration, has a metallic bronze appearance (9—13). 

Tris(0-ethyl dithiocarbonato)chromium(III) is obtained as a dark blue crystalline powder which decomposes at 100 to 140°. The indium(III) ethylxanthate complex forms small colorless crystals which decompose at 130 to 150°.16,17 The cobalt (III) ethylxanthate complex is isolated as a dark green crystalline powder whose decomposition temperature determined by use of a thermal balance is 135 to 137° (lit. value, 117° 2 118 to 119°8). These compounds decompose slowly in air and more rapidly when heated in solution. The tripositive chromium, indium, and cobalt complexes are insoluble in water but are soluble in many organic solvents (Table T). 

Chloro-triaquo-diammino-cobaltic Sulphate, [Co(NH3)2(H30)3 Ci]S04.H.,0, is obtained by decomposing an aqueous solution of acid dichloro-diaquo-diammino-cobaltic sulphate, [Co(b IIg)2(H20)2Cl2]S04H, with a small quantity of sulphuric acid and evaporating the solution in vacuo. It separates in indigo-coloured crystals and is soluble in water, giving a blue solution. 

That is, a mixture of 1-, 2-diaquo-tetrammino-cobaltic chloride and 1-, 2-diehloro-tetranimino-cobaltic chloride is formed. The aquo-salt is readily soluble in water but the diehloro-salt sparingly so. The last named forms intense blue crystals which are contaminated with small quantities of the praseo-salt, from which it may be freed by transforming it into the dithionate. The dithionate is practically insoluble, but the chloride may be regenerated from it by rubbing it with ammonium chloride. The bromide, the iodide, and the nitrate have all been prepared. 

Cobalt vapor interacts with norbornene to produce Co(C7H10)3, a 15-electron complex, apparently isostructural with Ni(C7H10)3. The cobalt complex is soluble in hydrocarbon solvents to afford deep blue solutions decomposing rapidly and autocatalytically at -15° (5a, 134). It has not yet been possible to isolate this complex in a pure state but some of the reactions have been examined by trapping experiments ... 

The color of the material is violet-brown. It is soluble in alcohol, ether, and acetone as well as esters to give a blue solution in each case—probably an auto-complex Co [Co (SON) 4]. In concentrated aqueous medium it is blue, but on dilution the color changes to the pink of hydrated cobalt (II) ions (dissociation of complex). 

Thirty grams of mercuric chloride and 44.5g of potassium thiocyanate are dissolved in 500ml of water and mixed with a solution of 20g of cobalt nitrate 6-hydrate in 50ml of water. A shower of small deep blue crystals of the difficultly soluble complex salt begins to form almost immediately. The mixture is allowed to stand for twelve hours to complete the predpitation and then suction-filtered. The product is washed with three 30ml portions of cold water, drained well, and then rinsed with two 25ml volumes of 95% alcohol to aid in drying. The material is dried in air or in the oven at 100° C. 

Coball(lI) hydroxide exists in two allolropic forms, a blue or-Co (OH) and a pink /l-Co(OH) . The hydroxide is prepared by precipitation from u cobaltous salt solution by an alkali hydroxide. When the alkali is in excess the pink ft form is produced—the blue a-furni is produced when the cobalt salt is in excess. The salt slowly oxidizes in air at mom temperature and changes to hydrated cobaltic oxide, Co-Oi - H 0. The hydroxide is practically insoluble in H 0 and in bases, but highly soluble in mineral and organic acids. The commercial salt is used as Ihe starting material in the preparation of drying agents. 

Wool and Polyamide Dyes. Water-soluble formazan complexes having sulfonamide, alkylsulfonyl, or sulfonic acid groups possess a high affinity to nitrogen-containing fibers. As with acid dyes, they can be used to dye wool and polyamide in neutral to weakly acid baths. Commercial dyes of this type are C.I. Acid Blue 267 and 297, and the 1 2 cobalt complex C.I. Acid Black 180, 13710 [11103-91-6] (29). 

In the cold the saturated solution is rose-coloured, like the crystalline hexahydrated salt. On warming it becomes violet between 25° and 50° C., above which latter temperature it is blue. This is explained by some as due to a change in hydration of the cobalt salt in solution from the red hexahydrate, through the violet monohydrate, to the blue anhydrous salt. Certainly the changes in colour correspond to breaks in the solubility curve as shown in Fig. I.1 A similar change in colour from red to blue likewise occurs with increase of concentration of the solution. 

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