The reasons of the success or phaseout of an industrial process remain mysterious. The history of the Perrin process allows to analyze this problem. After having described the process and the physical- chemical mechanisms underlying it, the author presents the good results obtained for the dephosphorization and the deoxidation of liquid steel and the problems which had to be solved in the case of desulphurization. Different aspects of the application of the process are discussed and different views on its adoption by steel producers are compared.