Abstract: An electrode system for voltametric measurements for measuring oxidative and reductive compounds in aqueous solutions primarily in the paper and pulp industries, said system comprising a working electrode (1), a counter-electrode (2) and a reference electrode (3), these being connected to a voltametric measuring apparatus (4). The aim is to introduce an electrode system mountable in the process pipeline with greater ease than electrodes of prior art and of a construction simpler than earlier systems, and more durable and less maintenance-requiring than these.As taught by the invention, the reference electrode (3) is a metal electrode and has been made for instance of silver, platinum, gold, titanium or "Hastalloy C" steel. The electrodes are advantageously installed together and in one and the same pick-up and disposed to be so placed in the process pipe system that the solution flowing in the pipe system flushes the electrodes.