LETTER OF TRANSMITTAL 



U. S. DEPARTMENT OF AGRICULTURE, 



DIVISION OF CHEMISTRY, 



Washington, 1). C., July .9, 1898. 



SIR: In accordance with your request of April 15, I have carefully 

 read the manuscript submitted by Prof. J. W. Mallet, being a result of 

 the investigation of analytical methods for distinguishing between the 

 nitrogen of proteidsaud that of the simpler amids or amido-acids. 



This investigation was undertaken by Professor Mallet at the sug- 

 gestion of the Office of Experiment Stations, and under the immediate 

 direction of the director of that office and of Prof. W. O. Atwater, 

 special agent. The work being purely of a chemical character, it was, 

 at your suggestion, and with the assent of Drs. True and Atwater, sub- 

 mitted to this office for inspection. The investigation consists in a 

 chemical study of the methods of quantitative analysis employed in 

 the separation of proteid and amid bodies, especially in animal prod- 

 ucts. The results are similar in their scope to the chapter on this sub- 

 ject contained in iny work on the Principles and Practice of Agricultural 

 Analysis, vol. 3. 



Professor Mallet has stated in an admirable manner the different 

 methods which have been proposed for the separation of proteid mat- 

 ters in animal products. By a happy modification, of the phospho- 

 tungstic acid method he has greatly improved this process, and shown 

 how a practical separation of the flesh bases from the other nitroge- 

 nous substances can be effected by this reagent. The flesh bases are to 

 some extent precipitated by the new form of the reagent proposed by 

 Professor Mallet, but they are brought into a soluble state by the addi- 

 tion of water and heat, so that a practically complete separation of 

 them is effected. This process, together with the use of taunic acid for 

 the separation of peptones, leaves little to be desired in securing a 

 practically complete separation of the nitrogenous matters. The ana- 

 lytical processes proposed have been thoroughly worked out by experi- 

 ment upon products of known composition, so that their reliability has 

 been by this means more firmly established. 



One of the most useful and simple methods of separating proteid 

 matters into insoluble and gelatinoid proteids, and of separating these 

 two classes from the flesh bases, is by the use of hot water, followed by 

 the use of chloriu or bromin a method not mentioned either in the 

 Principles and Practice of Agricultural Analysis, above referred to, 



