EXAMINATION OF FROZEN EGG PRODUCTS. 91 



high, fitted with a 2-hole rubber stopper carrying a right-angle air- 

 inlet tube, open at the bottom and extending to within h inch of 

 the bottom of the cylinder, and a trap containing either a cotton 

 or glass wool plug to prevent any liquid from being carried over me- 

 chanically. (4) A wide-mouthed 8-ounce bottle fitted with a de- 

 livery tube coming from the trap on the aerating cylinder. It is 

 not essential that the special ammonia absorption tubes be used. 

 An ordinary glass tube with a small bulb blown on the end through 

 which a few holes are punctured answers very well. The method of 

 making these is given by Folin and Farmer. 1 (5) A means of passing 

 air through the system. This is best done by a pump which will 

 furnish a blast with a pressure of 10 pounds per square inch and which 

 discharges into a tank of sufficient size to compensate for the pulsa- 

 tions of the pump and to deliver a steady blast. Suction may be 

 used, but it is not recommended. Each of the first four parts enumer- 

 ated is fitted with a 2-hole rubber stopper, and all are connected by 

 glass tubes of suitable shape and length to permit the proper passage 

 of air through the apparatus. The tube leading into the acid wash 

 bottle should contain a stop cock for regulating the air supply. 



Weigh approximately 25 grams of sample in a convenient con- 

 tainer. Pour as much as possible of this material into the aeration 

 cylinder, and transfer the remainder by means of four 25 cc. portions 

 of ammonia-free water, stirring each time with a rubber-tipped glass 

 rod to remove any egg adhering to the sides of the weighing vessel. 

 Add 75 cc. of alcohol, mix well, let stand for 15 minutes. Add 

 approximately 1 gram of sodium fiuorid, 2 cc. of 50 per cent 

 potassium carbonate solution, and 1 cc. of kerosene. Connect the 

 apparatus, and aerate into the receiving bottle, which should contain 

 10 cc. of N/50 sulphuric acid, 2 drops of methyl red indicator (satu- 

 rated solution in 95 per cent alcohol), and about 75 cc. of ammonia- 

 free water. The aeration should be carried on for 4 hours, or as 

 long as necessary to remove all of the ammonia, using as rapid a 

 current of air as possible. Titrate the excess of acid with N/50 

 sodium hydroxid (free from carbon dioxid). Express the results 

 obtained as milligrams of ammonia nitrogen per 100 grams of sample 

 on the wet basis. If there is insufficient time to complete the determi- 

 nation, the sample may be left over night in the cylinder with the 

 alcohol and sodium fiuorid added. The potassium carbonate, of 

 course, should not be added until ready to proceed. If the sample 

 has a bad odor it may be necessary to use more than 10 cc. of N/50 

 sulphuric acid. 



It is essential that a blank experiment be run to determine the 

 percentage recovery of ammonia, using a known amount of pure 



> J. Biol. Chem. (1912), 11 : 486. 



