28 MEAT EXTRACTS. 



METHODS OF ANALYSIS AND THEIR DISCUSSION. 



One of the great obstacles in the way of a thorough and careful 

 study of proteids is the unsatisfactory condition of the analytical 

 methods. Many of the variations in results which have appeared 

 are undoubtedly due to faulty methods. Another serious source of 

 error in this line of work lies in the fact that different methods are 

 used by different analysts and the results are not comparable. For 

 instance, copper oxid, phosphotungstic acid, tannic acid and salt, and 

 other reagents, are used by various workers to precipitate the higher 

 amido bodies and separate them from the simpler amido bodies. 

 That the precipitating power of these reagents is not the same is well 

 known. For determining acid and alkali albumins, insoluble proteid, 

 and coagulable proteid, the methods give only approximate results, 

 those for the determination of several of the individual bodies, such 

 as kreatin, kreatinin, and ammonia, being in a much more satis- 

 factory condition. 



PREPARATION OF SAMPLE. 



In the case of liquid and semiliquid preparations the bottle should 

 be thoroughly shaken and great care taken to see that the solution is 

 complete. Pasty and solid extracts or powders should be removed 

 from the container and thoroughly mixed before sampling. A very 

 convenient method is to dissolve a weighed sample in a measured 

 quantity of water and run this out of a burette as needed. This 

 solution should be kept cold and the determinations started without 

 delay. 



MOISTURE. 



Moisture was determined in the various preparations examined by 

 drying the sample over night in a ^ater-jacketed drying oven. In 

 the case of solid meat extracts approximately 3 grams of the sample 

 were used, for fluid extracts, 10 to 12 grams, and for meat powders, 2 

 grams. 



ASH. 



The ash content of the commercial samples is seen to be surprisingly 

 high in many cases. (See Tables II, IV, and IX.) This is due to the 

 fact that sodium chlorid is present in meat extracts in varying and 

 often excessive quantities. Especial attention is called to the large 

 percentage of sodium chlorid present in several of the samples exam- 

 ined. The figures reported in the tables are obtained by calculating 

 the total chlorin to sodium chlorid. 



The ash was determined by the official method a and the sodium 

 chlorid in the ash by the following procedure: 



Dissolve the ash sample with nitric acid and make up to volume in a 200-cc flask. 

 Use 20 per cent, or any convenient aliquot, for titration with sulpho-cyanid according 

 to the Vol hard method. 



«U. S. Dept. Agr., Bureau of Chemistry, Bui. 107, p. 38. 



