108 METHODS OF ANALYSIS. 



necessary, owing to the tendency of the latter to decompose. Reserve the fat 

 for examination according to the methods given under " XIX. Edible Oils and 

 Fats," page 129. Fat must be kept in a cool place and the examination finished 

 before it becomes rancid. 



4. Moisture. Provisional. 

 Proceed as directed under " VI. General Methods," page 38. 



5. Ash. Provisional. 

 Proceed as directed under " VI. General Methods," page 38. 



6. Ether Extract or Crude Fat. Provisional. 

 Proceed as directed under " VI. General Methods," page 39. 



7. Nitrogenous Substances. Provisional. 

 (a) TOTAL NITROGEN. 



Employ either the Kjeldahl or the Gunning method (as given under " I. Ferti- 

 lizers," p. 5) using about 2 grams of the fresh sample. The digestion with sul- 

 phuric acid should be continued at least four hours. 



(b) INSOLUBLE PKOTEIDS. 



Thoroughly exhaust 2 grams of the sample with cold water after extraction 

 with ether, filter, and determine nitrogen in the insoluble residue as directed 

 under "(a) Total nitrogen." Multiply the percentage of nitrogen so obtained 

 by 6.25 for the percentage of meat fiber or insoluble proteids. (In case the con- 

 nective tissue is determined, a corresponding correction must be made in the per- 

 centage of insoluble proteids. ) 



(c) CONNECTIVE TISSUE. 



i:\haust 10 grains with cold water as directed above, then boil the exhausted "j 

 residue repeatedly with about 100 cc of water until the total extract amounts to 

 approximately 1 liter. Filter, concentrate by evaporation, and determine the 

 nitrogen content. Multiply the nitrogen so obtained by fi.r.r* to obtain the per-, 

 centage of nitrogenous substances of connective tissue. 



(d) COAGULALLi: PROTEIDS. 



(For uncooked meat only.) 



. Almost neutralize the filtrate from the insoluble proteids, leaving it still I 

 faintly acid, boil until the coagulable proteids separate, filter, wash, transfer the 

 filter paper and contents to a Kjeldahl llask, and determine nitrogen as directed I 

 above under "(a) Total nitrogen." Multiply the percentage of nitrogen obtained 

 by 6.25 to obtain the percentage of coagnlable proteids. 



(e) I'KOTLOSI.S. PKITONES, AND GELATIN. 



Heat the filtrate from albumin and globulins, add a slight excess of tannic 

 acid and a few drops of a saturated solution of alum, allow to cool, filter, and 

 wash with cold water. Heat the filtrate from the taimic-acid precipitate almost 



