Cupric Colloidal

The action of an active intermediate oxidation product would explain another feature of the reaction. The reduction of silver ions by hydrazine is extremely sensitive to the presence of small amounts of copper. For example, a solution containing a mixture of silver nitrate, sodium sulfite and hydrazine which normally showed no sign of reduced silver for several minutes underwent almost immediate reaction when merely stirred with a clean copper rod. In the presence of gum arabic as stabilizer, streamers of colloidal silver passed out from the copper surface. Similarly, the addition of small amounts of cupric sulfate to a hydrazine solution eliminated the induction period of the reaction with silver chloride. 

Cupric sulfate exerts an effect on the silver chloride-hydroxylamine reaction similar in kind to that which it exerts on the hydrazine reaction, but in a smaller degree. If sufficient cupric sulfate is added to the hydroxylamine solution, the character of the reduction of silver chloride shifts towards that shown by the hydrazine reaction, e.g., the effect of gelatin becomes less pronounced, a minimum rate at a small gelatin addition is not obtained, and significant amounts of colloidal silver appear in the solution. 

In heavily sulfited white wines containing over 0.5 ppm copper and stored in sealed containers, a reddish-brown deposit may form. This occurs in the absence of oxygen and ferric ions but redissolves readily upon exposure to oxygen. Its formation may be accelerated by exposure to sunlight or heat, and it is believed to consist of colloidal cupric sulfide (14, 29). More commonly, copper casse may arise from reactions between copper and sulfur-containing amino acids, peptides, and proteins (15,16,17). 

Reaction of the sandwich-type POM [(Fc(0H2)2)j(A-a-PW9034)2 9 with a colloidal suspension of silica/alumina nanopartides ((Si/A102)Cl) resulted in the production of a novel supported POM catalyst [146-148]. In this case, about 58 POM molecules per cationic silica/alumina nanoparticle were electrostatically stabilized on the surface. The aerobic oxidation of 2-chloroethyl ethyl sulfide (mustard simulant) to the corresponding harmless sulfoxide proceeded efficiently in the presence of the heterogeneous catalyst and the catalytic activity of the heterogeneous catalyst was much higher than that of the parent POM. In addition, this catalytic activity was much enhanced when binary cupric triflate and nitrate [Cu(OTf)2/Cu(N03)2 = 1.5] were also present [148],... 

A. While stirring to produce a uniform dispersion, add about 1 g of powdered sample to 50 mL of warm water. Continue stirring until a colloidal solution is produced, and then cool to room temperature. Save part of this solution for Identification Test B. Add 10 mL of cupric sulfate TS to about 10 mL of the solution. A fluffy, blue-white precipitate forms. 

Cupric hydroxide, Cu(OH)2.—The hydroxide has been prepared in crystalline form by the action of a solution of caustic alkali on a basic cupric nitrate 2 and a basic cupric sulphate,3 and also by other methods.4 A hydrogel of varying composition is precipitated by addition of alkali to solutions of cupric salts.5 Unlike the colloidal form, the blue crystalline variety is stable at 100° C. A solid, colloidal variety has been obtained 6 as blackish-blue, brittle lamellae which dissolve in water to form the original solution. An amorphous modification is precipitated from ammoniaeal copper solutions by the action of alkali-metal hydroxides.7... 

In qualitative analysis copper is detected by precipitation as cupric sulphide from hydrochloric-acid solutions of its salts. To prevent the formation of a colloidal precipitate, the solution should be hot, and should contain excess of the acid. The sulphide is soluble in hot, dilute nitric acid, and in potassium-cyanide solution, but almost insoluble in solutions of alkali-metal sulphides. It dissolves to some extent in ammonium-sulphide solution. Other aids in the detection of copper are the blue colour of solutions of cupric-ammonia salts the reddish-brown precipitate of cupric ferrocyanide, produced by addition of potassium ferro-cyanide to cupric solutions the formation of an intense purple coloration by the interaction of hydrogen bromide and cupric salts, a very delicate reaction2 the formation of a bluish-green borax bead and the ready isolation of the metal from its compounds by the action of reducers. 

Silver subchloride, AgaCl.—When silver subfluoride is heated with phosphorus trichloride at 140° C., silver subchloride is formed.8 It is also a product of the interaction of silver nitrate and cuprous chloride, of a colloidal solution of silver and chlorine-water,9 and of silver-foil and weak oxidizers such as cupric chloride. 

Copper occurs in soil solids and solutions almost exclusively as the divalent cation Cu ". However, reduction of Cu " (cupric) to Cu (cuprous) and Cu (metallic copper) is possible under reducing conditions, especially if halide or sulfide ions ( soft bases) are present to stabilize Cu" (a soft acid). Copper is classified as a chalcophile, owing to its tendency to associate with sulfide in the very insoluble minerals, CU2S and CuS. In reduced soils, then, copper has very low mobility. Most of the colloidal material of soils (oxides of Mn, Al, and Fe, silicate clays, and humus) adsorb strongly, and increasingly so as the pH is raised. For soils with high Cu accumula-... 

Copper casse is specific to white wines. They are not as well protected from oxidation and reduction phenomena as red wines, where phenols have a redox buffer capacity. Furthermore, the colloidal cupric derivative contains proteins, while red wines have a low protein content due to combination reactions with phenols. 

Nugatory attempts to render the metal active by the addition of cupric chloride, sodium sulphite, alcohol, ferrous chloride, ferric chloride, colloidal platinum, chromic acid, potassium nitrite prolonged contact with metallic platinum variation of temp, between 0 and 50° previous treatment of the metal with chromic acid or potassium permanganate fusion with potassium nitrate heating on charcoal with sodium phosphate to give the metal a phosphorus content melting in the electric oven in an atm. of coal-gas using the metal as anode have all been made. 

The formation of (II) provides a quite selective spot test for palladium. Gold must be removed prior to the test because it will cause the development of a deep ruby red in the spot plate test and a diffused violet spot on the paper, apparently due to the reduction of the gold ions to the colloidal metal. Interference may also arise from 0s04 , Os+, Ru+, and RuCle ions because they have distinct self-colors. Mercurous ion causes partial interference by the reduction of part of the palladium to the elementary state, but a positive response can still be seen. It is possible to detect I part of palladium in the presence of 200 parts of platinum or 100 parts of rhodium. Less favorable ratios should be avoided because of the color of these salts. No interference is caused by mercuric and iridic chloride, but free ammonia, ammonium ions, stannous, cyanide, thiocyanate, fluoride, oxalate, and tetraborate ions do interfere. Lead, silver, ferrous, ferric, stannic, cobaltous, nickel, cupric, nitrite, sulfate, chloride, and bromide ions do not interfere. 

A. UltrafiUration. — By the use of filters that allow electrolytes to pass freely through, but retain the colloidal particles, colloidal stannic acid must have, after filtration, not only its ultramicrons, with their attendant anions, but also an equivalent amount of alkali ion molecules. The excess of the electrolytes, KOH, KaSnOa, etc., that were dissolved in the disperse medium, have passed through. The adsorbed portion of the alkali, regardless of whether it is dissociated or not, is an essential part of the hydrosol for if it is removed the colloid will coagulate. Duclaux, who has studied the behavior of colloidal iron oxide and cupric ferrocyanide in this connection, has proposed the name Micells for the ultramicrons together with their adsorbed molecules... 

Colloidal Salts. — In a great many other cases also the use of structural formulas serves to elucidate the processes and the reactions. In the chapters on colloidal salts other instances will be given. Here a single illustration will be taken up, viz the peptisation of cupric ferro-cyanide gel by potassium ferrocyanide. 

The cupric ferrocyanide colloidal particles adsorb the ferrocyanide ion, become negatively charged as a result and go into solution. 

Colloidal copper ferrocyanide can be made by pouring a dilute solution of copper chloride into a dilute solution of potassium ferrocyanide. The hydrosol thus formed is clear and has a reddish brown color. With increasing concentration of copper the solution becomes more and more turbid and finally such concentration relations are obtained that the hydrosol coagulates. This relation between the concentrations is not wh.at one would predict from a knowledge of the equivalents of the cupric and ferrocyanide ions, but as shown by Duclaux coagulation... 

For the cupric ion any other ion in equivalent amount may be substituted to cause the precipitation. This tendency of the colloid to adsorb the potassium ferrocyanide is important in analytical chemistry. It is evident that potassium ferrocyanide cannot be titrated with cupric chloride because the end point will be reached before an equivalent amount of cupric ion has been added. A great many other precipitates behave similarly and herein lies the reason that zinc salts cannot be titrated accurately with potassium ferrocyanide or sodium sulfide. 

Reddy, K.J., McDonald, K.J. King, H. (2013) A novel arsenic removal process for water using cupric oxide nanoparticles. Journal of Colloid and Interface Science, 397, 96-102. 

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