482 



Transactions. 



The results are shown as follows : — 



Ammoniacal Nitrogen expressed as Percentage of Total Nitrogen. 



Magnesium-oxide Folin's Aeration 



(1.) 



(2.) 

 (3.) 



(4.) 

 (5.) 

 (6.) 



(7.) 

 (8.) 



Average 



In a former paper (3) the ammoniacal nitrogen in freshly prepared 

 extracts was shown to average 7-06 per cent, of the total nitrogen, using 

 the magnesium-oxide method. 



It will thus be seen that even after six months' storage and after 

 ordinary atmospheric exposure no decomposition is found by either method. 



Ammonia Test for Spoilage of Solutions of Meat-extracts. 



fn a former paper it was shown that the ammoniacal nitrogen deter- 

 mined by the magnesium-oxide method increases markedly in known cases 

 of decomposition of meats, and it was established that this method was 

 capable of demonstrating incipient decomposition (1). As, however, the 

 magnesium-oxide distillation method is somewhat empirical — because if a 

 further quantity of water is added to the solution in the distillation -flask, 

 and another 100 c.c. are distilled, it will be found that the distillate con- 

 tains a further amount of ammonia — it has been customary to determine 

 the ammonia in the first 100 c.c. of the distillate only. It is apparent 

 that, in addition to liberating the loosely bound ammoniacal nitrogen, the 

 magnesium oxide is capable of producing hydrolysis, with the result that 

 ammonia is being continuously split off from the nitrogenous compounds. 

 Our experiments confirm those of others, that after four hours' continuous 

 aeration at a rate of 80 litres of air per hour little, if any, ammoniacal 

 nitrogen is liberated by continuing the aeration. 



In order to determine whether the aeration method is applicable to 

 the determination of ammoniacal nitrogen in known cases of decomposition 

 of aqueous solutions of meat-extract, solutions of various dilutions were 

 prepared and contaminated by exposure to the ordinary bacteria of decom- 

 position present in the air. The results of the determinations of the 

 ammoniacal nitrogen by the aeration method are as follows : — 



Ammoniacal Nitrogen expressed as Percentage of Total Nitrogen. 



After 9 days 

 After 10 days 

 After 11 days 



It is thus seen that the method is capable of detecting decomposition 

 of dilute solutions of meat-extract, and it is therefore applicable in the 



