Red-brown

Cd(OH) j. The hydroxide is precipitated from aqueous solution by OH", it does not dissolve in excess OH". Ignition of Cd(OH)2 or CdCO, gives CdO which varies in colour from red-brown to black because of lattice defects. 

Karathane A trade name for 2,4-dinitro-6-( 1 -methylheptyl)phenyl crotonate, CJ8H24N2O6, a compound which has both acaricidal and fungicidal activity. It is a red-brown oil of high boiling point, insoluble in water but soluble in most organic solvents. Karathane is used for the control of powdery mildew, and is nontoxic to mammals. 

Sm ( —2-41 volts in acid) SmXj (SmX3 + Sm) are red-brown in colour, SmO is formed similarly. 

The halides known are yellow TcF and TcFs (both Tc and Fj). Red-brown TeCU (Tc -f CI2) is the only known chloride. Oxides Tc20t, TCO3 and TCO2 are known. The complexes are similar to those of Re K2TcHg is known. 

Both the acid and its salts are powerful reducing agents. They reduce, for example, halogens to halides, and heavy metal cations to the metal. Copper(H) ion is reduced further to give copper(I) hydride, a red-brown precipitate ... 

Vanadium pentoxide, vanadium(V) oxide, V2O5, is the most important compound in this oxidation state. It is a coloured solid (colour due to charge transfer, p. 60), the colour varying somewhat (red -> brown) with the state of subdivision it is formed when vanadium (or some of its compounds) is completely oxidised, and also by heating ammonium vanadate)V) ... 

The V(IV) species are all d complexes, hence their colour. Besides the VO compounds, some halides VX4 are known, for example VCI4, a liquid with a tetrahedral, covalent molecule and properties similar to those of TiCl4, but coloured (red-brown). 

If an aqueous solution of an iron(lll) salt is treated with alkali, a red-brown precipitate of iron(III) hydroxide is obtained this is probably best represented as FeO(OH). On strong heating it gives the red oxide Fe203. Iron(III) oxide, Fc20, occurs naturally as haematite, and can also be prepared by strong heating of iron(II) sulphate ... 

The solid readily dissolves chemically in concentrated hydrochloric acid, forming a complex, and in ammonia as the colourless, linear, complex cation [H3N -> Cu <- NHj] (cf AgCl) if air is absent (in the presence of air, this is oxidis to a blue ammino-copper(II) complex). This solution of ammoniacal copper(I) chloride is a good solvent or carbon monoxide, forming an addition compound CuCl. CO. H2O, and as such is used in gas analysis. On passing ethyne through the ammoniacal solution, a red-brown precipitate of hydrated copper(I) dicarbide (explosive when dry) is obtained ... 

To a few drops of the ester, add 0 2 g. of hydroxylamine hydrochloride and about 5 ml. of 10% NaOH solution and gently boil the mixture for 1-2 minutes. Cool and acidify with HCl, cool again and then add a few drops of FeClj solution. A violet or deep red-brown colour develops immediately. 

Place 10 ml. of 1% starch solution (prepared as described above) in a boiling-tube, add 2 ml. of 1% sodium chloride solution and place the tube in a water-bath maintained at 38-40 . Place about 5 ml. of water in a series of test-tubes and to each add a few drops of 1% iodine solution. Now add 4 ml. of the diluted saliva solution to the starch solution, mix well and note the time. At intervals of about 30 seconds transfer 2 drops of the reacting mixture, by means of a dropping tube, to one of the test-tubes, mix and note the colour. As in the previous experiment, the colour, which is blue at first, changes to blue-violet, red-violet, red-brown, pale brown, and finally disappears at this stage the solution will reduce Fehling s solution. If the reaction proceeds too quickly for the colour changes to be observed, the saliva solution should be diluted. 

Phthalide. In a 1 litre bolt-head flask stir 90 g. of a high quality zinc powder to a thick paste with a solution of 0 5 g. of crystallised copper sulphate in 20 ml. of water (this serves to activate the zinc), and then add 165 ml. of 20 per cent, sodium hydroxide solution. Cool the flask in an ice bath to 5°, stir the contents mechanically, and add 73-5 g. of phthalimide in small portions at such a rate that the temperature does not rise above 8° (about 30 minutes are required for the addition). Continue the stirring for half an hour, dilute with 200 ml. of water, warm on a water bath imtil the evolution of ammonia ceases (about 3 hours), and concentrate to a volume of about 200 ml. by distillation vmder reduced pressure (tig. 11,37, 1). Filter, and render the flltrate acid to Congo red paper with concentrated hydrochloric acid (about 75 ml. are required). Much of the phthalide separates as an oil, but, in order to complete the lactonisation of the hydroxymethylbenzoic acid, boil for an hour transfer while hot to a beaker. The oil solidifles on cooling to a hard red-brown cake. Leave overnight in an ice chest or refrigerator, and than filter at the pump. The crude phthalide contains much sodium chloride. RecrystaUise it in 10 g. portions from 750 ml. of water use the mother liquor from the first crop for the recrystaUisation of the subsequent portion. Filter each portion while hot, cool in ice below 5°, filter and wash with small quantities of ice-cold water. Dry in the air upon filter paper. The yield of phthalide (transparent plates), m.p. 72-73°, is 47 g. 

Prepare the reagent by dissolving 7 -5 g. of sodium iodide in 50 ml. of A.R. acetone. The colourless solution gradually acquires a yellow colour. Keep it in a dark bottle. When a red-brown colour develops, it should be discarded. 

Nitramine, picrylmethylnitramine, 2,4,6-trinitrophenylmethyl nitramine (indicator) dissolve 0.1 g in 60 mL alcohol and dilute with water to 100 mL pH range colorless 10.8-13.0 red-brown the solution should be kept in the dark as nitramine is unstable on boiling with alkali it decomposes quickly. Fresh solutions should be prepared every few months. 

Bromine Monofluoride. Bromine monofluoride is red to red-brown (4) and is unstable, disproportionating rapidly into bromine and higher fluorides. Therefore, the measurement of its physical properties is difficult and the values reported in Table 1 are only approximate. The uv-absorption spectmm is available (25). 

Some treatments are practiced so widely that untreated material is essentially unknown ia the jewelry trade. The heating of pale Fe-containing chalcedony to produce red-brown carnelian is one of these. Another example iavolves turquoise where the treated material is far superior ia color stabiUty. Such treatments have traditionally not been disclosed. Almost all blue sapphire on the market has been heat treated, but it is not possible to distinguish whether it was near-colorless comndum containing Fe and Ti before treatment, or whether it had already been blue and was only treated ia an attempt at marginal improvement. The irradiation of colorless topa2 to produce a blue color more iatense than any occurring naturally is, however, self-evident, and treatments used on diamond are always disclosed. 

Sulfides. The main sulfide of indium is I1I2S2 [12030-24-9], which can be prepared by heating the metal with sulfur or by precipitation from weak acid solutions of indium salts by H2S. Precipitated I1I2S2 varies in color from yellow to red-brown, and in crystal size depending on formation conditions. It dissolves in acids and sodium sulfide solution. Other reported sulfides of indium ate InS [12030-14-7], a red-brown soHd In2S [12196-52-0], and In S [12142-00-5]. 

The parent acid of the hexakiscyanoferrate(3—) salts is ferricyanic acid [17126464] (trihydrogen hexakiscyanoferrate). Red-brown needles are obtained by evaporation of solutions prepared by adding sulfuric acid to tribarium bis(hexakiscyanoferrate). The acid is used to prevent metal surface corrosion. 

Fumarates. lron(Il) fumarate [141 -01 -5], Fe(C4H20, is prepared by mixing hot aqueous solutions of sodium fumarate and iron(Il) sulfate followed by filtration of the resulting slurry. It has limited solubiUty in water but is more soluble in acid solution. The compound is red-orange to red-brown and finds uses as a hematinic. A non stoichiometric compound [7705-12-6] and iron(Ill) fumarate [52118-11-3], Fe2(C4H20 3, are also available. 

Iron(III) hydroxide [1309-33-7], FeH02, is a red-brown amorphous material that forms when a strong base is added to a solution of an iron(III) salt. It is also known as hydrated iron(III) oxide. The fully hydrated Fe(OH)3 has not been isolated. The density of the material varies between 3.4-3.9 g/cm, depending on its extent of hydration. It is insoluble in water and alcohol, but redissolves in acid. Iron(III) hydroxide loses water to form Fe203. Iron(III) hydroxide is used as an absorbent in chemical processes, as a pigment, and in abrasives. Salt-free iron(III) hydroxide can be obtained by hydrolysis of iron(III) alkoxides. 

A triperoxymanganate(IV), K2H2Mn0(02)2, is said to be formed (40) when KMnO in 30% KOH is treated with H2O2 at — 18°C. It is a dark red-brown crystalline compound, which in water slowly evolves O2 and precipitates Mn02. In the dry state this material is explosive above 0°C, but under... 

PurpurogaHin (5), a red-brown to black mordant dye, forms from electrolytic and other mild oxidations of pyrogaHol (1). The reaction is beHeved to proceed through 3-hydroxy-(9-benzoquinone (2) and 3-hydroxy-6-(3,4,5-trihydroxyphenyl)-(9-benzoquinone (3). The last, in the form of its tautomeric triketonic stmcture, represents the vinylogue of a P-diketone. Acid hydrolysis leads to the formation of (4), foHowed by cyclization and loss of formic acid... 

Ana.lytica.1 Methods. Thiocyanate is quantitatively precipitated as silver thiocyanate, and thus can be conveniendy titrated with silver nitrate. In the presence of a ferric salt, a red-brown color, produced by the ferric thiocyanate compex, indicates the end point. 

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