Chemical analysis is effected by automatic titration of a soln., in which an electrical potential Em, coming from e.g. indicator and reference electrodes in the soln., is compared to a defined potential Ec. The improvement is that the potential Ec is modified during the titration according to a programme of specified duration until it has reached a final value Ec(fin). The modification is carried out either by successive steps or continuously. The number, the duration and the amplitude of the steps, or the law governing the continuous change, are fixed in advance or chosen by the operator according to the analysis being carried out. The difference Em-Ec is used to control the rate U of generation or addn. of the titrating species. The rate is further dependent on the value of the derivative dEm/dt, where t-time, and the difference between Em(or Ec) and a comparison potential E(comp). The relation is of the form U = k(Em-Ec)x(Em-E comp)y(dEm/dt)z + m. The values k, Ec, x, Ecomp, y,z,m can be fixed in advance or controllable by the operator, it being specified that x,y are not negative, z is not positive, x,y, z are not O simultaneously, m is not negative, k is not zero. Method is suitable for large and small quantities of liq and ensures that the quantity of titrating species cannot exceed that defined by the stoichiometry of the reaction. The analytical programme, e.g. over 24 hours, can be chosen in advance, and the precision is constant.
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