Ammonia electrolytes

Another mechanism for induced codeposition of Mo was suggested by Chassaing et al for electrodeposition of Mo-Ni alloys from citrate-ammonia electrolytes. Electrochemical impedance spectroscopy (EIS) measurements were carried out in order to better understand the different reactions occurring on the electrode surface during deposition. The proposed mechanism is based on a multi-step reduction of molybdate species. A M0O2 layer is formed via reduction of molybdate ion as in Eq. (42). Then, if free Ni is present in solution, this oxide can first combine at low polarization with Ni, following the reduction reaction ... 

PZC/IEP of Magnetite Obtained from Sulfate and Ammonia Electrolyte T Method Instrument pHo... 

PZC/IEP of Ni(OH), Obtained from Nitrate and Gaseous Ammonia Electrolyte T Method Instrument pH Reference... 

CB Ross, T Wada, RM Crooks, DM Smith. Electrochemical synthesis of metal nitride ceramic precursors in liquid ammonia electrolyte solutions. Chem Mater 3 768, 1991. 

Fuels which have been used include hydrogen, hydrazine, methanol and ammonia, while oxidants are usually oxygen or air. Electrolytes comprise alkali solutions, molten carbonates, solid oxides, ion-exchange resins, etc. 

Hydroxylamine is derived from ammonia by replacing one hydrogen atom by a hydroxyl group. It is prepared by the electrolytic reduction of nitric acid, using a lead cathode ... 

The ammonia values can be recycled or sold for fertilizer use. The most important consideration ia this process is the efficient elimination of the phosphoms from the product, because as Htfle as 0.01% P2 5 electrolyte causes a 1—1.5% reduction ia current efficiency for aluminum production (28). 

Manufacture and Economics. Nitrogen tritiuoride can be formed from a wide variety of chemical reactions. Only two processes have been technically and economically feasible for large-scale production the electrolysis of molten ammonium acid fluoride and the direct fluorination of the ammonia in the presence of molten ammonium fluoride. In the electrolytic process, NF is produced at the anode and H2 is produced at the cathode. In a divided cell of 4 kA having nickel anodes, extensive dilution of the gas streams with N2 was used to prevent explosive reactions between NF and H2 (17). 

The covalent character of mercury compounds and the corresponding abiUty to complex with various organic compounds explains the unusually wide solubihty characteristics. Mercury compounds are soluble in alcohols, ethyl ether, benzene, and other organic solvents. Moreover, small amounts of chemicals such as amines, ammonia (qv), and ammonium acetate can have a profound solubilizing effect (see COORDINATION COMPOUNDS). The solubihty of mercury and a wide variety of mercury salts and complexes in water and aqueous electrolyte solutions has been well outlined (5). 

A newer approach developed for producing commercial quantities of high purity AP (8,36) involves the electrolytic conversion of chloric acid [7790-93 ] to perchloric acid, which is neutralized by using ammonia gas ... 

Hydrogen Liquefaction. Hydrogen can be produced from caustic—chlorine electrolytic cells, by decomposition of ammonia or methanol, or by steam—methane reforming. Hydrogen recovered by these methods must be further purified prior to Hquefaction. This is generally achieved by utilizing pressure swing adsorption methods whereby impurities are adsorbed on a soHd adsorbent. 

The electrolytes used were acetate buffer at pEI values 2, 4 and 6 and the same electrolyte is used in the presence of EDTA at pEI values of 2 and 6. Iron and copper contents could be most easily determined in EDTA medium at pH 6. The best medium for nickel was found to be as ammonia buffer pH 9.5 qg/L, it could be separated from zinc in this medium. The elements determined in white and red wine were Cu, Pb, Zn, Cd, Fe and Ni. The quantities found were for iron about 9000 qg/L, for copper 290 qg/L, Ni 80 qg/L, lead 150 qg/L and zinc 460 qg/L. The validation was made by determining each element under different conditions. 

Industrially, chlorine is obtained as a by-product in the electrolytic conversion of salt to sodium hydroxide. Hazardous reactions have occuned between chlorine and a variety of chemicals including acetylene, alcohols, aluminium, ammonia, benzene, carbon disulphide, diethyl ether, diethyl zinc, fluorine, hydrocarbons, hydrogen, ferric chloride, metal hydrides, non-metals such as boron and phosphorus, rubber, and steel. 

In the most common hydrometallurgical process, the ore is leached with ammonia or sulfuric acid to extract the copper. These processes can operate at atmospheric pressure or as pressure leach circuits. Copper is recovered from solution by electrowinning, a process similar to electrolytic refining. The process is most commonly used for leaching low-grade deposits in situ or as heaps. 

Constitution. On electrolytic reduction cytisine yields tetrahydrode-oxycytisine, C44H20N2, an alkaline oil, b.p. 270°, yielding a crystalline hydrochloride, B. HCl, m.p. 282°, [aju — 10-25°. With phosphorus and hydriodic acid cytisine furnishes ammonia and cytisoline, C41H44ON,... 

Sulfamide, (H2N)2S02, can be made by ammonolysis of SO3 or O2SCI2. It is a colourless crystalline material, mp 93°, which begins to decompose above this temperature. It is soluble in water to give a neutral non-electrolytic solution but in boiling water it decomposes to ammonia and sulfuric acid. The structure (Fig. 15.50c)... 

As we have pointed out, strong acids and bases are completely ionized in water. As a result, compounds such as HC1 and NaOH are strong electrolytes like NaCl. In contrast, molecular weak acids and weak bases are poor conductors because their water solutions contain relatively few ions. Hydrofluoric acid and ammonia are commonly described as weak electrolytes. 

The products of this electrolysis have a variety of uses. Chlorine is used to purify drinking water large quantities of it are consumed in making plastics such as polyvinyl chloride (PVC). Hydrogen, prepared in this and many other industrial processes, is used chiefly in the synthesis of ammonia (Chapter 12). Sodium hydroxide (lye), obtained on evaporation of the electrolyte, is used in processing pulp and paper, in the purification of aluminum ore, in the manufacture of glass and textiles, and for many other purposes. 

Weak acids with weak bases. The titration of a weak acid and a weak base can be readily carried out, and frequently it is preferable to employ this procedure rather than use a strong base. Curve (c) in Fig. 13.2 is the titration curve of 0.003 M acetic acid with 0.0973 M aqueous ammonia solution. The neutralisation curve up to the equivalence point is similar to that obtained with sodium hydroxide solution, since both sodium and ammonium acetates are strong electrolytes after the equivalence point an excess of aqueous ammonia solution has little effect upon the conductance, as its dissociation is depressed by the ammonium salt present in the solution. The advantages over the use of strong alkali are that the end point is easier to detect, and in dilute solution the influence of carbon dioxide may be neglected. 

Reagents. In view of the sensitivity of the method, the reagents employed for preparing the ground solutions must be very pure, and the water used should be re-distilled in an all-glass, or better, an all-silica apparatus the traces of organic material sometimes encountered in demineralised water (Section 3.17) make such water unsuitable for this technique unless it is distilled. The common supporting electrolytes include potassium chloride, sodium acetate-acetic acid buffer solutions, ammonia-ammonium chloride buffer solutions, hydrochloric acid and potassium nitrate. 

Ni is found in many ores in combination with S, As Sb, the chief sources being the minerals chalcopyrite, pyrrhotite and pentlandite. Ni ores are of two types, sulfide and oxide, the former accounting for two-thirds of the world s consumption. Sulfide ores are refined by flotation and roasting to sintered Ni oxide, and either sold as such or reduced to metal, which is cast into anodes and refined electrolytically or by the carbonyl (Mond) process. Oxide ores are treated by hydrometallurgjcal refining, eg, leaching with ammonia. Much secondary Ni is recovered from scrap (Refs 6 7) 1... 

If copper is present in the boiler FW (normally as the cupric ammonia complex ion), boiler surfaces are directly attacked by electrolytic reduction. In strongly alkaline conditions the ferrous ion is present as ferrous hydroxide [Fe(OH)2] ... 

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