36 MASS. EXPERIMENT STATION BULLETIN 378 



Other service rendered included the analysis of cocoa for iron, the 

 qualitative examination of material found to be limestone, and the de- 

 termination of the strength of a commercial sample of formaldehyde. 



Carotene and chlorophyll were determined in two standard samples 

 and one local sample (spinach and alfalfa) by several methods as col- 

 laborative work on A. O. A. C. methods for these constituents in feed- 

 stufTs. 



Testing Analytical Methods. (The Department.) In furtherance of 

 the collaborative work on zinc in foodstuffs under the auspices of the 

 A. O. A. C, samples of white dent corn (Johnson County Ensilage) and 

 of spinach (Burpee's Victoria), together with granulated zinc for stand- 

 ardizing, were sent to analysts who had expressed a willingness to take 

 part. Results by the Massachusetts method were promising, on the whole, 

 but revealed some possible errors in technique that could be easily rem- 

 edied. The suggestions for the coming year call for additional investigation 

 to insure greater accuracy and easier operation as follows: 



1. Complete solution of the zinc in hydrochloric acid. 



2. Prevention or at least reduction of contamination by the glassware. 



3. Use of dithizone in carbon tetrachloride when a suitable colorimeter 

 and filters are available for a "mixed color" method. 



4. Adoption of a specific color filter for the determination. 



The Iron, Copper, Zinc, and Iodine Content of Fruits and Vegetables 

 Used as Human Food. ( E. B. Holland, C. P. Jones, and W. S. Ritchie.) 

 The analyses of some 324 foodstuffs conducted during the past few years 

 have now been completed. The analyses include proximate constituents 

 and trace metals in fruits, vegetables, cereals, nuts, processed human and 

 cattle feeds, and roughage. 



Lignin and Its Relation to the Absorption of Minerals by Plants. ( Em- 



mett Bennett.) A thorough description of the objectives of this project 

 has appeared in previous annual reports. 



Last year it was noted that when corncob lignin was dispersed in sodium 

 hydroxide and titrated electrometricall}^ with a strong acid, data were ob- 

 tained which, when plotted, produced a titration curve having two inflec- 

 tion points — one at about pH 4.5 and the other at about pH 8.0. A study 

 was made of the conditions necessary to reproduce this curve. Such 

 behavior is indicative of the activity of definite chemical groups. In some 

 instances data may be obtained from titration curves which may be of 

 assistance in determining the nature of the active groups. From the data 

 obtained in this study "apparent dissociation" constants were calculated. 

 These values were found to be comparable to the dissociation constants of 

 substances containing phenolic hydroxyl and weak carboxyl groups. This 

 relative agreement, however, is not conclusive evidence of the presence 

 of phenolic hydroxyl and carboxyl groups in the material tested. 



A study of the base exchange capacity of purified lignin indicated a 

 low value. However, solution in alkali followed by precipitation and sub- 

 sequent electrodialysis increased the exchange value many times. The 

 enhanced value of the specially prepared lignin was reduced to the level of 

 that of the original by drying at about 80°C. The enhancement in capacity 

 is believed to be due chiefly to increased state of hydration made possible 

 by previous treatment. 



