Electrometer definition

In all of these checks the electrometer showed no deflections below the critical potential, while above this critical potential a very definite deflection was obtained. 

The two-half cells contain the aqueous substrate. The mixed monolayers are spread onto the surface of one of the two-hetlf cells. Two "identical" 24lAm 0.7 mCi ionizing electrodes, purchased from the Radiochemical Center Amersham (U.K.), are placed above the hedf cells close to the substrate surface. The difference in electric potenticd of the two electrodes is measured with a high impedence electrometer. By definition this difference is equal to the surface potentietl AV of the monolayer located on the surface on one of the two-hedf cells. The surface potential AV is measured as a function of the spread monolayer molecular area a for each one of the mixed film compositions as above (see surface pressure studies). 

The position of the mercury meniscus in the capillary depends on the surface tension between the mercury and the sulphuric acid and this, in turn, depends on the electrical potential between the mercury and the acid. If this potential is altered, as, for example, by connecting the two mercury electrodes with a cell or with two points of a circuit between which there is a difference of potential, the meniscus will movej and for small differences of potential, the amount of movement is proportional to the difierence of potential. In order, however, that the meniscus shall take up a definite position, the two electrodes must be connected together except when making a measurement This is efiected by means of a triple contact Morse key, shown in Fig. 72. The electrical connections between the terminals a, b, c and the contacts d, V, d are indicated by means of the dotted lines. The electrodes of the electrometer are connected with the terminals b and c, so that they are connected together when the key is in its normal position. The terminals a and c are connected with the rest of the circuit, so... 

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