ANNUAL REPORT, 1938 33 



hurricane materially added to the confusion associated with this disease. The 

 reddish discoloration of new growth is the chief characteristic of the disease. 



Other serious problems arising from the hurricane in matters relating to tree 

 diseases and their carrier insects may demand attention during the next growing 

 season. Especially, the danger of a material increase in the bark beetles which 

 carry the causal fungus of the Dutch elm disease must not be overlooked in view 

 of the favorable beetle breeding conditions created by large quantities of stored 

 elm wood from which the bark has not been removed. 



DEPARTMENT OF CHEMISTRY 



W. S. Ritchie in Charge 



Cooperative Analytical Service. (The Department.) Chemical service to out- 

 side agencies was not extensive and involved only a comparison of the manganese 

 content of four chick feeds, the determination of copper in two soils, and the 

 analysis of a mineral lick and two brine solutions. 



Testing Analytical Methods. (The Department.) The perfection of methods 

 of analysis is an important project and this work has been carried on especially 

 with zinc, since the laboratory has been acting as an associate referee fo zinc, 

 cooperating with the A. O. A. C. The method was reported in the May 1938 

 issue of the journal of the above organization. This method shows practically 

 complete recovery of zinc between 5 and 25 gammas. For larger amounts of 

 zinc, smaller aliquots are recommended rather than a development of a different 

 procedure. This method was studied with solutions of the ash of various food- 

 stuffs, obtained for other projects, to which had been added known amounts of 

 zinc. While the method seems practical and gives accurate results, it was deemed 

 advisable to study the reaction of solutions of pure salts of various, and possibly 

 interfering, metals with the carbamate and dithizone reagents. Solutions of the 

 following metals (as chlorides) were compared with these reagents singly and 

 (in a few cases) in various combinations: aluminum, antimony, beryllium, bismuth, 

 cadmium, cerium, chromium, cobalt, copper, gold, iron, lead, manganese, mer- 

 cury, nickel, palladium, platinum, silver, thallium, thorium, tin, uranium, van- 

 adium, zinc, and zirconium. The results obtained confirmed the belief that the 

 proposed method was applicable for most foodstuflfs. 



A method for the determination of boron by titration using two indicators 

 (methyl red and phenolphthalin) has proved workable but somewhat difficult 

 because of the low boron content of most foods. 



The Iron, Copper, Manganese, and Iodine Content of Fruits and Vegetables. 



(E. B. Holland, C. P. Jones, and W. S. Ritchie.) For some time, evidence has 

 been accumulating in the scientific literature, that the so-called minor elements 

 play a much more important role in nutrition and health than has been heretofore 

 suspected. Perhaps many of the difficulties of both man and animal may be 

 laid to a lack of one or more of these elements. It seemed important, therefore, 

 that the information regarding these elements in fruits, vegetables, and cereal 

 products used for human and animal foods be brought up to date, using the 

 more improved methods of analysis. 



Sixty-three samples were added to the several hundred already under inspec- 

 tion. Some of these came from the Waltham Field Station, others from the 

 market gardeners of eastern Massachusetts and were produced under different 

 cultural practices of fertilization and on various types of soil. The samples showed 

 an appreciable range of ash constituents and the more prominent food groups 

 (by proximate analysis). 



