KINETICS OF DISSOLUTION OF NICHROME IN HYDROCHLORIC-ACID

Nichrome is extensively used in heating elements in industrial furnace s and metallurgical industries. In this investigation, studies were ca rried out to determine the dissolution characteristics of nichrome in hydrochloric acid, with or without their respective salts, at various concentrations, Nickel and chromium in dissolved nichrome solution wer e analysed using atomic absorption spectrophotometry. The dissolution studies were conducted at different concentrations of hydrochloric aci d, ranging from 0.5 to 6.0 M and also in mixtures of hydrochloric acid and sodium chloride (1.0-3.5 M), keeping the HCl concentration consta nt at 1.0 M. The effect of temperature (40-100 degrees C) on the disso lution of nichrome in 6.0 M HCl for different periods is also reported . The activation energy was found to be 58.6 kJ/mol. The results of th e kinetic study have been used to elucidate the mechanism of the proce ss by applying Langmuir's adsorption isotherm. The experimental result s confirm the mechanism that both hydrogen and chloride ions are respo nsible for the dissolution process. In simple hydrochloric acid, the h ydrogen ion is rate controlling, whereas in mixtures of hydrochloric a cid and excess amounts of sodium chloride, the chloride ion is respons ible for determining the rate of dissolution. In low concentrations of hydrochloric acid (0.04-0.22 M) and high concentrations of sodium chl oride (1.0-4.0 M) the observed constancy in the rate of reaction has b een attributed to saturation of the active sites of the nichrome surfa ce by the chloride ion.