APPENDIX J 153 



After cooling, dilute with about 200 cc. of water, add a few pieces 

 of granulated zinc or pumice stone, if necessary in order to keep 

 the contents of the flask from bumping, and add 25 cc. of potas- 

 sium sulphide solution with shaking. Next add 50 cc. of the soda 

 solution, or sufficient to make the reaction strongly alkaline, pouring 

 it down the side of the flask so that it does not mix at once with the 

 acid solution. Connect the flask with the condenser, mix the con- 

 tents by shaking, and distill until all ammonia has passed over into 

 the standard acid. The tip of the condenser should dip into a 300-cc. 

 Erlenmeyer flask containing 20-40 cc. of standard acid and enough 

 distilled water to make a depth of 1-2 cm. The first 150 cc. of 

 the distillate will generally contain all the ammonia. This operation 

 usually requires from forty minutes to one hour and a half. The dis- 

 tillate is then titrated with standard alkali, using cochineal as the in- 

 dicator. Each cubic centimeter of decinormal ammonia is equivalent 

 to 1.4 mg. of nitrogen. 



