CONTENTS XlX 



Chemical Techniques (continued) 



C. Filters 176 



D. Stirring Devices 178 



E. Heating Devices 180 



F. Moist Chambers 181 



G. Electrodes 183 



H. Conductivity Apparatus 188 



I. Balances 189 



II. Colorimetric Techniques 195 



A. Capillary Tube Technique 195 



1. Apparatus 196 



2. Manipulations 197 



3. Methods 198 



Preparation of Protein-Free Supernatants 198 



Tungstic Acid Supernatants 198 



Trichloroacetic Acid Supernatants 199 



Zinc Sulfate-Sodium Hydroxide Supernatants 200 



Chloride 200 



Westfall, Findley, and Richards Method for Chlorides 200 



Sodium 203 



Bott Method for Sodium 203 



Phosphate 208 



Walker Method for Phosphate 208 



Phosphatase 209 



Weil and Russell Method for Phosphatase 209 



Reducing Substances 210 



Walker and Reisinger Method for Reducing Substances 211 



Creatinine 211 



Method of Bordley et al. for Creatinine 211 



Uric Acid 213 



Bordley and Richards Method for Uric Acid 213 



Urea 214 



Walker and Hudson Method for Urea 214 



Hydrogen Ion Concentration 216 



B. Cuvette Technique 216 



1. Apparatus '. 216 



2. Methods 219 



Calcium 219 



Sendroy Method for Calcium 219 



Chloride 224 



Sendroy Method for Chloride 225 



Phosphate and Phosphatase 226 



Lundsteen and Vermehren Method for Inorganic Phosphate 



and Phosphatase 227 



Lowry and Lopez Method for Inorganic Phosphate in 



Presence of Labile Phosphate Esters 228 



Bessey, Lowry, and Brock Method for Phosphatase 229 



Nitrogen and Ammonia 230 



General ; 230 



Digestion of Sample for Determination of Total Nitrogen ...234 



Le\'y Nesslerization Method for Nitrogen 237 



Russell Phenol-Hypochlorite Method for Ammonia 238 



Uric Acid, Creatine, Creatinine, and AUantoin 239 



Borsook Method for Uric Acid 240 



Borsook Method for Creatine and Creatinine 242 



Sure and Wilder Method for Creatine and Creatinine 243 



Borsook Method for AUantoin 243 



