38 MASS. EXPERIMENT STATION BULLETIN 347 



hydroxide, and then compared to a standard prepared in the same manner. 

 Such a method shows practically a complete recovery between 5 and 25 gammas 

 of zinc. For larger amounts of zinc, the use of suitable aliquots of the sample 

 was recommended rather than the development of a different procedure. Details 

 of the method will appear in the Journal of the A.O.A.C. 



Methods for the determination of boron are now under consideration since it is 

 becoming more and more evident that this element is a factor to be considered 

 in certain crops, and methods for measuring small amounts are necessary. 



Vitamin C (ascorbic acid) ma 3' be determined satisfactorily in comparison with 

 the bio-assay by titration with a dye, 2, 6-dichlorophenolindophenol. The dye has 

 usually been standardized against either pure ascorbic acid or lemon juice. A 

 new method has been devised for the standardization of the dye, agreeing very 

 well with the two methods above, based on the quantitative oxidation of iodide 

 to iodine. The iodine liberated is titrated with standard sodium-thiosulfate. 

 This method is much simpler, involving only one titration, once the standard 

 solution of sodium-thiosulfate is prepared. This method was presented and dis- 

 cussed at the recent meeting of the American Chemical Society at Rochester, 

 New York, and will appear, in abstract, in the journals of that organization. 



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

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

 project, having for its objective an analytical survey of common foods, including 

 grains, fruits, vegetables, nuts, etc., has been continued. Sixty-two new samples 

 have been collected and prepared for the analysis which is under way. The 

 proximate analysis is being determined as well as the content of iron, manganese, 

 copper, iodine, phosphorus, and zinc. 



With the cooperation of the workers at the Waltham Field Station, it has been 

 possible to get samples of vegetables including celery, beets, carrots, cabbage, and 

 spinach, whose history is known, i.e., the soil type producing them, fertilizer 

 treatment, irrigation, and other cultural practices. It is expected that such 

 samples will reflect the influence of these treatments assuming that there is an 

 effect. 



Approximate Range in Some Ash Constituents 

 In Terms of Dry Matter 



Crude Ash Iron Copper Manganese Phosphorus 

 ppm ppm ppm ppm 



Acid Acid 



Soluble Insoluble 



Major fruits....!- 3.5 0.00-0.03 10- 80 5-15 tr.- 10 200-1800 



Berries 1-5 0.00-0.25 40-180 5-40 20-170 600-2900 



"Garden" fruits 4-11 0.00-0.15 20-130 5-40 tr.- 35 1200-5000 

 Leaf and stem 



vegetables.. . 9-23 0.02-2-f 25-1000 5-35 tr.-250 3000-10000 



Root vegetables 4-15 0.02-0.10 20-200 5-40 tr.- 35 1400-5000 



Cerealsi 1-3 0.00-0.50 30-120 5-15 tr.- 60 900-4500 



Nuts 2-4 0.00-0.01 tr.- 150 5-25 10-45 2500-7500 



Peas and beans 4-8 0.00-0.10 75-100 5-25 10-35 4500-7000 



^Excluding unhulled grains. 



The completion of the analyses of the samples now in the process should, with 

 a few additional ones, finish this survey. 



