Fill the Hittorf Cell with 0. Remove the electrodes from coulometer, rinse with distilled water then alcohol, dry them and weight them at the end of the electrolysis. This is checked with the coulometer in the circuit.
After the electrolysis, measure the total volume of anode compartment. Waste container of experiment: Take 25 ml from middle compartment, add 5 ml 6 M HNO 3, 50 ml distilled water and 1 ml ferric ammonium sulfate, and titrate this solution with KSCN up to a first permanent red tint color.
In electrolysis, the concentration of the electrolyte in the middle compartment does not change, while it changes in the anode and the cathode compartment. Electrodes are inserted into the cathode and anode chambers.
The apparatus consists of two separated compartments joined by a substantial middle compartment, a coulometer, and an AC-DC converter as shown in Figure 1. However, due to migration of ions, the concentration of the solution in the anode chamber and in the cathode chamber has changed but that in the middle chamber remains unchanged Figure.
In other words, for each anion passing a given plane in the solution there will be three cations passing in the opposite direction. Fill the coulometer with CuSO 4 solution. The mobility of an ion is defined as its velocity in the direction of an electric field of unit strength i.
Determination of Transference Number by Group Number: Take 25 ml from anode compartment, add 5 ml 6 M HNO 3, 50 ml distilled water and 1 ml ferric ammonium sulfate, and titrate this solution with KSCN up to a first permanent red tint color.
Wash them with distilled water and then with alcohol. The decrease in the amount of electrolyte at the anode is three times greater than that at the cathode. Since the initial concentration of the AgNO3 is known the fall in concentration in cathode an anode chambers are calculated.
The exceptions are hydrogen and hydroxyl ions with the abnormally high mobilities of The mobility of ions is generally quite small in the order of 6x m 2.
The method of measurements may be illustrated by the determination of transport number of silver and nitrate ions. As a result of passing the current electrolysis takes place, Ag is deposited on the cathode and dissolved in the anode.
Assistant name and Signature: The transport number tube is filled with a dilute AgNO4 solution of exactly known concentration 0. In part III three pairs of ions remains in the anode compartment and five pairs in the cathode one. Among the factors associated with the nature of the ions are its charge and size.
Polish the copper plates and silver electrodes with sand paper. Ionic mobilities are important factors in many electrochemical phenomena. Construct the cell in a serial connection. Before the electrolysis the concentration of the electrolyte in all compartments is the same, each compartment contains six pairs of ions which is shown part I of Figure 2.
From the time and the current the total quantity of electricity in Coulomb passed through the solution is calculated.The cation transport number of the leading solution is then calculated as + = +, where + is the cation charge, the concentration, the distance moved by the boundary in time, the cross-sectional area, the Faraday constant, and the electric current.
The transference number of an ion-constitu- ent n thus considers the overall effect of the trans- port of charged species a, b, c etc. which contain n, and the transference number may be related to the transport numbers of the individual species.
Membrane transference numbers from a new emf method Magnar Ottay, Tormod Frarland, Slgne Kjelstrup RatkJe and Steffen Moller-Holst Keywords transference number, ion exchange membranes, emf measurements Introduction Rapld and precise methods to obtain mem- brane transference coefficients are important.
Measurement of Transference Number. Transference Number may be measured by different methods, e.g., Hittorf’s method, moving boundary method and from the electromotive force of concentration cells. Here briefly focus on Hittorfs method-This method is based on the measurement of change in the concentration of the electrolyte.
Methodology The reagents used for this experiment were the following: * Methyl red * M Nitric Acid * M Copper sulfate – sulfuric acid mixture. Transport Number Or Transference Number Transport Number or Transference Number (1) Definition: “ The fraction of the total current carried by an ion is known as transport number, transference number or Hittorf number may be denoted by sets symbols like t + and t – or t c and t a or n c and n a ”.Download