During the nineties many experiments on water chlorination were made by Traube, Sickenberger, Kauffman, Berge, Bassenge, and others. Traube[15] was able to completely sterilise water rich in bacteria in 2 hours by the addition of bleach equal to 1.06 p.p.m. of available chlorine. At the end of the contact period about 90 per cent of the added chlorine was unabsorbed and was destroyed by the addition of sodium bisulphite. Bassenge[16] followed up the work of Traube and that of Sickenberger and Kauffman, who had shown that it was possible to destroy cholera vibrio in Nile water by means of sodium hypochlorite. Bassenge used higher concentrations than Traube and found it possible to destroy _B. typhosus_ and _B. coli_ in ten minutes with 60-90 p.p.m. of available chlorine. The excess was destroyed by adding calcium bisulphite. Lode[17] experimented with waters seeded with _B. coli_, _B. typhosus_, and _B. tetani_ and found, contrary to Traube, that 1-2 p.p.m. of chlorine did not sterilise in two hours. _B. coli_ was usually destroyed by 4 p.p.m. of chlorine in ten minutes and even better results were obtained with _B. typhosus_ and cholera vibrio: the former was destroyed in one hour by 1 p.p.m. and in ten minutes by 2 p.p.m.; the latter organism required 1-2 p.p.m. with a twenty-minute contact period. Lode noted that organic matter lowered the bactericidal activity of chlorine and recommended the use of 30 p.p.m. of chlorine to ensure rapid and complete sterilisation. Berge[18] used chlorine peroxide, generated by the action of hydrochloric acid on potassium chlorate, for the sterilisation of water and this process was afterwards used at Ostend at a plant having a capacity of about 1,300,000 gallons per day. The dosage was equal to 0.53 p.p.m. of available chlorine and coke filters were used to destroy the excess although they were not found to be indispensable as the free chlorine disappeared spontaneously. This process appears to have been tried on the Brussels supply and also for the treatment of a hospital supply at Petrograd. The object of German sanitarians seems to have been to obtain practically instantaneous sterilisation of water for the use of travellers and troops in the field. Until the commencement of the European War they did not have a high opinion of chlorination and generally regarded it as inefficient. Schumberg[19] expressed the opinion that no chemical method of disinfection could be absolutely relied upon, under all circumstances, to prove fatal to bacteria. Plucker[20] stated that several investigators, particularly Schuder, had shown that chlorine, even in the proportion of 40 p.p.m. did not invariably destroy cholera vibrio and _B. typhosus_; and that with smaller doses the destruction was still less complete. He also stated that the bacteriological experiments of American workers were open to criticism and that they employed antiquated methods.