MAINE SARDINE INDUSTRY. • 13 



In the same way, by grinding and mixing through the meat chopper, prepare the 

 contents of the cans. Wipe the last traces of oil from the interior of the can with the 

 ground fish. 



MOISTURE. 



Spread thinly 2 or 3 grams of sample in 2J-inch lead-foil caps, and dry in vacuo 

 (25 to 28 inches) for 5 hours at 55° C. 



Extract the dried residues from the moisture determinations for from 12 to 15 hours 

 in a Knorr fat extraction apparatus with 50 cc of absolute ether, prepared over sodium. 

 Evaporate the ether at as low a temperature as possible, and dry the ether extract 

 1 hour at 55° C. in vacuo. 



ACIDITY OF FAT(9). 



Dissolve the dried ether extract residues in 50 cc of benzol. Add 2 drops of phenol- 

 phthalein and determine the acidity by titrating with N/20 sodium ethylate. Calcu- 

 late the acidity as cc of N/20 sodium ethylate per 1 gram of fat. 



TOTAL NITROGEN. 



Determine by the Gunning modification of the Kjeldahl method (A. O. A. C. 

 Methods, 1916, p. 7). 



AMMONIA NITROGEN. 



Nessler(8) - 1 — Weigh 3-gram samples and transfer to large test tubes, or small Kjeldahl 

 flasks, with 20 to 25 cc of water. Add 3 cc of 10 per cent solution of potassium carbon- 

 ate, 3 cc of 15 per cent solution of potassium oxalate, and a little heavy cylinder oil. 

 Pass a strong current of ammonia-free air through this mixture for four hours. Collect 

 the ammonia in 5 cc of N/20 sulphuric acid contained in a 100-cc volumetric flask. 

 After aerating, dilute the contents of the flask to the 100-cc mark. Transfer a 25-cc 

 aliquot portion to a 100-cc volumetric flask and dilute nearly to the mark. After 

 adding 2 cc of Nessler solution and making to volume, compare the density of the 

 color of the solution in a Duboscq colorimeter with that of a known standard. 



Titration. — Weigh 3-gram samples and transfer to large test tubes, or small Kjeldahl 

 flasks, with 20 to 25 cc of water. Add 3 cc of 10 per cent solution of potassium carbon- 

 ate, 3 cc of 15 per cent solution of potassium oxalate, and a little cylinder oil. Force 

 a strong current of ammonia-free air through this mixture for four hours. Collect the 

 ammonia in 5 cc N/20 sulphuric acid, in a 100-cc volumetric flask. After aeration, 

 titrate the excess acid in the flasks with N/50 alkali, using methyl red as the indicator. 



TOTAL VOLATILE NITROGEN FOR THE SEPARATION OF AMMONIA AND AMINES. 



Weigh thirty 3-gram samples into tubes of the Folin apparatus, or small Kjeldahl 

 flasks, arranged for the aeration method for the determination of ammonia. To each 

 add about 25 cc ammonia-free water, a pinch of sodium fluorid, 3 cc of 15 per cent 

 potassium oxalate, and 3 cc of 10 per cent potassium carbonate. Aerate four hours. 

 Collect the alkaline volatile nitrogen compounds in 5 cc of N/20 sulphuric acid. 

 After the necessary time has elapsed, remove the flasks, and titrate back with N/50 

 potassium hydroxid. Use methyl red for the indicator. The acid used is equivalent 

 to the total volatile nitrogen, that is, the sum of the ammonia and amines present. 



1 Although a number of determinations of ammonia by the Nessler method were made, they are reported 

 in only a few of the tables. The term "ammonia," as used in the tables and text, represents the total 

 volatile alkaline material (ammonia and amines) as determined by the titration method. In the decompo- 

 sition studies, and the work on the formation of ammonia and amines here reported, the total volatile 

 alkaline bases are separated into the amines and ammonia. In the work on the decomposition of the 

 copepods (feed), and on the influence of the temperature of storage on the formation of ammonia and amines, 

 the amines were further separated into their three classes by a method recently devised. 



