STANDARD METHODS FOR THE EXAMINATION OF WATER AND SEWAGE _FOURTH EDITION_ Revised by committees of the American Public Health Association, American Chemical Society, and referees of the Association of Official Agricultural Chemists AMERICAN PUBLIC HEALTH ASSOCIATION 169 MASSACHUSETTS AVENUE BOSTON 1920 _Copyright, 1917 and 1920_ _By the American Public Health Association_ ------------------------------------------------------------------------ CONTENTS. PAGE PREFACE TO THE FOURTH EDITION vii COLLECTION OF SAMPLES 1 QUANTITY OF WATER REQUIRED FOR ANALYSIS 1 BOTTLES 1 TIME INTERVAL BETWEEN COLLECTION AND ANALYSIS 2 REPRESENTATIVE SAMPLES 3 PHYSICAL EXAMINATION 4 TEMPERATURE 4 TURBIDITY 4 TURBIDITY STANDARD 4 PLATINUM WIRE METHOD 5 TURBIDIMETRIC METHOD 7 COEFFICIENT OF FINENESS 8 COLOR 9 COMPARISON WITH PLATINUM-COBALT STANDARDS 9 COMPARISON WITH GLASS DISKS 10 COMPARISON WITH NESSLER STANDARDS 10 LOVIBOND TINTOMETER 11 ODOR 12 COLD ODOR 12 HOT ODOR 12 EXPRESSION OF RESULTS 12