LABORATOKY BACTEKIOLOGY. 



APPENDIX B. 



METHODS. 



1. Kjeldahl Method for Total Nitrogen. 



1. Eeagents. 



(a) Standard HCl. 



Approximately one-half normal. The absolute 

 strength is determined by precipitating with 

 silver nitrate and weighing the silver chlorid 

 formed. 



(6) Standard Alkali (NH.OH). 



Approximately one-tenth normal. Standardize 

 against the HCl. 



(c) Potassium Sulfid solution. 



40 gms. KaS per liter of water. 



(d) Sodium Hydroxid. 

 A saturated solution. 



(e) Indicator. 



3 gms. cochineal digested in a mixture of 50 

 ce. alcohol and 200 cc. distilled water for 2 

 days and filtered. 



2. Determination. 

 (a) Digestion. 



The substance to be analyzed is placed in a 

 Kjeldahl flask with 0.7 gms. Hg. and 20 cc. 

 H2SO4 and heated in an inclined position until 

 all the organic matter is oxidized and the 

 nitrogen changed to (]SrH4),S04. 



