Carbamide melts

Our investigations showed that in mixed melts of eutectic composition carbamide-NH4(K)Cl, the oxidation and reduction of melt constituents take place mainly independently of each other. The anodic process at platinum electrodes in the range of potentials below 0.9V is associated with the direct oxidation of carbamide to secondary and tertiary amide compounds, accumulation of ammonium ions in the melt, and evolution of the same gaseous products as in carbamide electrolysis [8], The cathodic process is accompanied by the formation of ammonia, CO, and C02, i.e. of the same products as in pure- carbamide electrolysis. In contrast to carbamide melt, a large amount of hydrogen appears in the cathode gases of the mixed melt, and in the anode gases of the carbamide-KCl melt, the presence of chlorine has been established at potentials above 0.9V. In the... 

Use of low-temperature molten systems for electrolytic processes related with tantalum and niobium and other rare refractory metals seems to hold a promise for future industrial use, and is currently of great concern to researchers. The electrochemical behavior of tantalum, niobium and titanium in low-temperature carbamide-hilide melts has been investigated by Tumanova et al. [572]. Electrodeposition of tantalum and niobium from room/ambient temperature chloroaluminate molten systems has been studied by Cheek et al. [573],... 

The fifth paper in this chapter is by S. Kochetova and N. Tumanova of the National Academy of Sciences of Ukraine. It addresses subjects of electrolysis of molten carbamides. Authors report on interesting results of their study of the mechanisms of reactions occurring in the carbamide and carbamide-chloride melts using techniques of cyclic voltammetry in combination with gas chromatography and IR spectroscopy. 

ELECTROLYSIS OF CARBAMIDE-CHLORIDE MELTS AT INERT ELECTRODES... 

In an individual molten carbamide, the electrode processes are feebly marked at melt decomposition potentials (Fig. 1) because of its low electrical conductivity. Both electrode processes are accompanied by gas evolution. 

However, the physicochemical properties of nitrogen chloride give no grounds for the explanation of its stability under melt electrolysis conditions. The possibility of the formation of a chlorine derivative of carbamide according to the scheme ... 

Figure 3. Cyclic voltamperogram of Pt-electrode in carbamide-NH4Cl (curve 1) and in carbamide-KCl (curve 2) melts.

Figure 4. Differential capacity of Pt electrode in carbamide-NH4Cl melt (curve 1) and after 0.5 (curve 2), 1 (curve 3), 1.5 (curve 4), 2 (curve 5) hours of electrolysis.

In an individual molten carbamide, the electrode processes are feebly marked at melt decomposition potentials because of its low electrical conductivity. Both electrode processes are accompanied by gas evolution (NH3, CO, C02, N2) and NH2CN (approximately) is formed in melt. In eutectic carbamide-chloride melts electrode processes take place mainly independently of each other. The chlorine must evolve at the anode during the electrolysis of carbamide - alkali metal and ammonium chloride melts, which were revealed in the electrolysis of the carbamide-KCl melt. But in the case of simultaneous oxidation of carbamide and NH4CI, however, a new compound containing N-Cl bond has been found in anode gases instead of chlorine. It is difficult to fully identify this compound by the experimental methods employed in the present work, but it can be definitely stated that... 

Tumanova N. Electrochemistry of Nb, Ta and Ti in carbamide based melts. Proceedings of the Green Industrial Applications of Ionic Liquids. NATO Science Series. Ed. R. Rogers, K. Seddon, S. Volkov. Kluwer Academic Publishers, 2003. 

Tumanova N., Volkov S., Kochetova S., Triphonova T., Buryak N. Passivation and redox processes of refractory metals in carbamide-chloride melt. J. Mining and Metallurgy, 2003 39 69-81. 

Tumanova N., Babenkov E., Boyko O., Buryak N. The peculiarities of electrochemical niobium dissolution in carbamide based low-temperature melts. Abstracts of the 195-th... 

Tumanova N., Babenkov E., Chemuhin S. and others. Electrochemical properties of carbamide-halide melts. Ukr. Chim. J., 2000 66 35-9 (in Russian). 

Volkov S., Tumanova N., Kochetova S., Buryak N. The polysurface Mechanism of Ta and Ti Anodic Dissolution in Low-Temperature Carbamide-NELtCl Melt. Z. Naturforsh,... 

Raw stock methylphenyldichlorosilane (not less than 99% of the main fraction) methyl alcohol (not less than 0.5% of humidity) technical carbamide (urea), which is a colourless crystal substance with the melting point of 132-135 °C (not less than 0.2% of humidity) oil or coal toluene (the boiling point is 109.5-111 °C, d/° - 0.865 0.002) activated coal (not less than 0.02% of humidity). 

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