363 a standard alunlmum nitrate SolutuXr in aqueous buffer solutions (PH bctwccn 3.6 and 4 6) Equilibrium was c~tabhshed withm ~5 mm. The fluoride-aluminum ratio at the (true) end-point was found to mcreasc from z z m x0-4 M fluoride to 2 8 in 2 -IO -3 M fluoride. The titration calculated from the stability constants of the vanous aluminum-fluoride complexes wcrc found to bc in excellent agreement with the experimental curves. From a practical point of view titration m an acetate buffer in 50% alcohol in the prcsencc of o 5 M potassium or sodium mtratc is rccommendcd. The fluoride-alummum ratio at the end-point was found to be 5 9 & o 1 and independent of the fluoride concentration. RtiSUMl? L'Blectrodc rotativc d'alummmm peut dtre utihsec pour lc titragc amp&ombtnquc dcs fluorures, au moycn d'une solution &talon de mtratc d'alummlum. Lcs courbes de tltragc, calculdcs B partn dcs constants-de stabmt6 dcs divers complcxcs alumtmum-fluorurc, corrcspondcnt tr&s *hien aux courbcs cxp6rimcntalm ZUSAMMENFASSUNG Es wnd die Eignung dcr rotlcrenden Alumlniumelcktrode zur amperomctnschcn Bestimmung von Fluorld mlt cmcr Alumin~ummtratlOsung bcschricbcn 111~ auf dcr Davis der Stabllltatllconstanten dcr vcrschlcdcnen Alummium-Fluor:d Komplexcn bcrcchncten 'Tltrationskurvcnstimmcn sehr gut mit den exporlmcntell erhaltcncn Kurven ubcrem. REFERENCES 1 1 M 1COLTHOPFAND C. J SAMDUCI:TTI,~~~I~.