Galvanometer solution

Procedure. Pipette 25.0 mL of the thiosulphate solution into the titration cell e.g. a 150mL Pyrex beaker. Insert two similar platinum wire or foil electrodes into the cell and connect to the apparatus of Fig. 16.17. Apply 0.10 volt across the electrodes. Adjust the range of the micro-ammeter to obtain full-scale deflection for a current of 10-25 milliamperes. Stir the solution with a magnetic stirrer. Add the iodine solution from a 5 mL semimicro burette slowly in the usual manner and read the current (galvanometer deflection) after each addition of the titrant. When the current begins to increase, stop the addition then add the titrant by small increments of 0.05 or 0.10 mL. Plot the titration graph, evaluate the end point, and calculate the concentration of the thiosulphate solution. It will be found that the current is fairly constant until the end point is approached and increases rapidly beyond. 

By adjusting the potentiometer to a reading V such that the galvanometer indicates no current flowing when a is moved relative to the solution, conditions are created such that there is no field between a and the solution and thus... 

Cavendish, a century before, had attempted to compare quantitatively the electrical conductivity of rain water with various salt solutions. Possessing no galvanometer to register the strength of the currents, he had bravely converted his own nervous system into one. As he discharged Leyden jars through the different liquids he compared the electric shocks which he received. With this crude, heroic method he obtained a number of surprisingly accurate results. 

With pH-meters based on the principle of compensation, the operations are similar to those mentioned above, but the potentiometer knob (with the pH-scale) is set to a position corresponding to the pH of the buffer, and the galvanometer zeroed with the buffer adjustment knob. When the test solution is measured, the galvanometer is zeroed with the potentiometer knob, and the pH of the solution read from its scale. 

As the boundary moved down the U-tube, the resistance of the solution increased the galvanometer deflection was kept constant by decreasing the variable resistances. The movement of the boundary was followed with a travelling microscope, and the time taken to reach successive graduations was recorded on a stop-watch. Immediately after the experiment the galvanometer was calibrated to get an accurate value of the current used. The measurements and results are tabulated below. 

Attempt to Measure Total Quantity of Ozone Produced. In an earlier paper (S) the change of the total amount of light emitted by the oxidation of a certain quantity of luminol by sodium hypochlorite was studied as a function of the pH. For a pH of approximately 10, the reaction is complete and almost instantaneous. The authors attempted to make a dosage with luminol as it was oxidized by ozone after a paper disk was treated with an excess of sodium hypochlorite solution and to measure the light by means of a photometric setup, including a ballistic galvanometer. 

The excess Rayleigh ratio Rg can be derived from the raw galvanometer readings Ig and Igg when the sample container contains die solution and the solvent, respectively, with the photocell of Fig. 4.11 positioned at an angle 9 in both cases. Hie equation used is... 

Figure 4.12 The variation of effective scattering volume (shaded) with angle. A, incident beam B, polymer solution or solvent C, scattering cell D, light trap E, scattered light beam F, movable photocell connected to galvanometer.

ZZ are two zinc electrodes immersed in the solution the cell is placed in a thermostat and the zinc electrodes connected udth a galvanometer. Since at temperatures below the transition point the solubility of the hexahydrate (the metastable form) is greater than that of the heptahydrate, a current will be produced, flowing in the cell from heptahydrate to hexahydrate. As the temperature is raised towards the transition point, the solubilities of... 

For force measurements in a liquid medium, the L-shaped holder is used to mount particle a (Fig. IX-18). The horizontal part of the holder with the particle is immersed into liquid medium, while the vertical part is mounted to the extension of rotating axle of the galvanometer. With such a setup the meniscus at air-solution interface (around the holder) does not create any additional momentum and thus does not influence the measurements. 

---