An electrometric titration method for water determination, using the Karl Fischer reagent

Ionization of oxyphosphoranes. Phosphonium ions and hexacoordinated phosphorus anions

“…and X4 + X¿ = Aq', 103K = c( Ao*! + Ao'K3c)/VkiC + K3c2 (13) From the definition of K& (eq 4) and of A, it follows that *a = c(A/A0)2 = c( 10 3 / )2 (14) Equations 13 and 14 lead directly to eq 5 for the special case under consideration. The approximation of eq 5 by eq 7 has already been given.…”

Improvement in Karl Fischer Method for Determination of Water

“…To avoid this difficulty, the addition of excess Fischer reagent and back-titration with standard water in methanol solution to the dead-stop end point is frequently recommended (9, 12). Modifications of the dead-stop apparatus, employing increased potential across the electrodes (2) or increased current (3), have been reported to be satisfactory for the direct titration with Fischer reagent, and an automatic titration apparatus incorporating a timer mechanism which distinguishes between transitory currents produced by temporary excesses of unconsumed Fischer reagent and the true end point has been described (6) and marketed.…”