58 Cold-Storage of Fish [Oct. 



water, total solids, organic matter, inorganic matter ; second — ammonium 

 nitrogen, total nitrogen, " soluble nitrogen," " insoluble nitrogen," " co- 

 agulable nitrogen," " non-coagulable nitrogen;" third — lipins (per cent 

 and acidity) ; fourth — reducing substances and acidity of aqueous 

 extract. 



1. The determination of ivater was made in the following manner: 

 An accurately weighed sample, approximately 5 gm., was dried in a 

 large porcelain crucible on a water bath for from three to four hours, 

 after which it was placed in an air bath, at 110° C, and dried to con- 

 stant weight. 



In the determination of ash, the following precaution was taken to 

 prevent volatilization of Chlorides. After the organic matter had been 

 completely charred over a low flame, an aqueous extract was made of 

 the residue. This liquid was brought to the boiling point and allowed 

 to cool somewhat, when it was decanted as caref ully as possible through 

 an ashless filter, most of the residue remaining in the crucible. After 

 drying, the residue and filter were ignited over a bunsen burner to a 

 white ash. The extract was then added to the residue in the crucible 

 and evaporated to dryness on a water bath. Finally the crucible was 

 heated over a low flame to remove residual carbonaceous matter. By 

 this method the soluble salts were not subjected to the high heat of 

 ignition. 



Both total solids and organic matter were calculated from data 

 obtained by the foregoing methods. 



2. Ammonium nitrogen was determined by the following modifica- 

 tion of Folin's method.^^ Fifty grams of fish muscle were ground in a 

 mortar with sand. The finely ground meat was suspended in a mix- 

 ture of equal volumes of 95 per cent alcohol and water in an aeration 

 cylinder. The mixture of alcohol and water was used in order to 

 prevent excessive frothing during aeration. The volume in each case 

 was approximately 200 c.c. Fifty gm. of pure sodium chloride and 4 

 gm. of pure sodium hydroxide were added to each 200 c.c. of Suspen- 

 sion. As soon as the alkali was added, very vigorous aeration was 

 begun and continued for at least four hours. 



Total nitrogen was determined by the Kjeldahl process. Oxidation 

 was facilitated by the addition of a small piece of crystallin copper Sul- 

 fate to the sulfuric acid. 



13 Steel and Gies : Journal of Biological Chemistry, 1908, v, p. 71 ; Steel : 

 Ibid., 1910, viii, p. 365 ; Shulansky and Gies : Biochemical Bulletin, 1913, iii, p. 45. 



