Electrical Differential Method of Measurement in Electrotitrations Ap p 1ica t io n to Pot ent io me t r ic Titr a t io ns 1' \ C L l)EL.AlI \Y,C-nizersity of Oregon, Eugene, Ore.
The charging or discharging current of a condenser connected to the terminals of a potentiometric cell is maximum in the neighborhood of the end point of a titration. Laboratory devices and experimental results are described here.
D
to end point of titration, ml.; 8 is concentration of reagent, gram equivalent per liter; CY is rate of addition of the reagent (this rate is supposctl t o be constant in Equation 2), ml. per second; L is solubility product of compound A C ; C is capacity of condenser of measuring circuit, farad; and i is indicator current, ampere. As tht, curve i = f (v) is symmetrical with respect to the straight line of rquation v = n, the variations of the indicator current do not n t w l to be calculated after the end point.
IHECT determinations of the end points of potrhntioinetric titrations have usually beeii obtained by diffewntial niethods involving mechanical devices. Raker and Miiller ( 1 ) were the first to propose a differential method of ni(:asurt~nient baqed t ) n the properties of electrical circuits:. ~ I O I~Y w t ~ n tthe l y author (2, .?1 which is ,has described a general mc~thodof nic~xsui~c~mt.iit suxntnaiized here.
8.0
8.5 8.7 Milliliters
8.2
9.0
9.2
Figure 1. Variations of Indicator Current in Titration of Silver Nitrate Solution bj- Sodiirni Chloride Solution Volume of analvzed solution. 100 inl. Concentration-Gfreaient, 0.671 eq
