 In the 19th century, German chemist, Carl Remigius Fresenius suggest the solution to overcome this problem.Then rubber policeman also recorded in 1910 edition of J. C. Olsen's textbook of quantitative analysis that states ""...particles adhering to the glass must be removed by means of a so-called policeman, which is made by inserting the end of a rather thick large-sized glass stirring-rod into a short piece of rubber tubing.The rubber tube should be left protruding slightly beyond the end of the glass tube and sealed together with a little bicycle [i.e.