COHEN, B. and CLARK, W. M. The growth of certain bacteria in media of different hydrogen-ion concentrations. _Jour. of Bact._, 4, 1919, 409. Bibliography 232: FENNEL, E. A. and FISHER, M. A. Adjustment of culture medium reactions. _Jour. of Inf. Diseases_, 25, 1919, 444. Bibliography 233: JONES, H. M. A rapid hydrogen-ion electrode method for the determination of hydrogen-ion concentrations in bacterial cultures or other turbid or colored solutions. _Jour. of Inf. Diseases_, 25, 1919, 262. INDEX. A. Acidity, determination of, 39. Acids, mineral, 41. Agar, nutrient, 94, 96. lactose-litmus, 97. Alkali carbonates, 39. Alkalinity, determination of, 35. Albuminoid nitrogen, 20. Aluminium sulfate, determination of, 41. analysis of, 78. Aluminium and iron, determination of, 57. Ammonia nitrogen, determination of, 15. Apparatus, bacteriological, 93. Application of colon group tests, 102. Arsenic, determination of, 63. Azolitmin solution, 96. B. Bacillus aërogenes, reactions, 108. cloacae, reactions, 108. coli, reactions, 108. B. coli group, tests, 100. application of, 102. fecal and non-fecal, 106. summary of tests, 104. Bacteriological examination, 93. bibliography, 110. Basicity ratio, 80. Bibliography, bacteriological, 110. chemical, 82. microscopical, 91. Biochemical oxygen demand, 71. in sludge and mud, 76. Bismuthate method (Mn), 49. Boric acid, 63. Bottles, sample, 1, 93. dilution, 93. Bromine and iodine, determination of, 61. Broth, nutrient, 95. sugar, 95. C. Calcium, determination of, 57. Carbon dioxide, determination of, 40. Chemical analysis, water and sewage, 1. bibliography, 82. Chemicals, analysis of, 77. Chloride, determination of, 41. Chlorine, determination of, 64. Coefficient of fineness, 8. Collection of samples, bacteriological, 93. chemical, 1. Colon group, tests (see “B. coli”), 100. Color, determination of, 9. Copper, determination of, 53, 55. Counting (bacterial), 99. Cultural characters of colon group, 108. Culture media, 94. azolitmin solution, 96. Endo’s medium, 97. litmus-lactose-agar, 97. litmus solution, 96. methyl red test, 107. nutrient agar, 96. nutrient broth, 95. nutrient gelatin, 96. sterilization, 95. sugar broth, 95. titration, 94. tryptophane broth, 107. D. Dilution (bacteriological), 98. Dissolved oxygen, 65. E. Effluents, relative stability of, 69. biochemical, oxygen, demand of, 71. Endo’s medium, 97. Erythrosine indicator, 36. Ether—soluble matter, 69. in sludge and mud, 75. Evaporation, 29. Expression of results (see under “Results”). F.