ANNUAL REPORT, 1936 35 



copper, iron, manganese, and phosphorus. These likewise were not materially 

 affected although the manganese seemed to show a seasonal variation. Samples 

 were dried and are being held for further inorganic analysis. 



The separation of the nitrogen fractions soluble in a 10 percent sodium chlo- 

 ride solution indicated that although there was no appreciable difference between 

 the commercial fillets, regardless of the method of freezing, there was a decrease 

 in the amount of soluble nitrogen during storage. While there was no increase 

 in the amount of ammonia nitrogen in any of the samples during storage at 

 low temperatures, a very definite correlation is apparent between the amount 

 of ammonia and the length of time that either fresh or defrosted samples were 

 held at temperatures above freezing. 



Assays for vitamins A and D indicated that, although haddock muscle is 

 not an important source of these nutritional constituents, both are present in 

 measurable amounts and are apparently not affected by freezing. 



Chemical Changes in Cooking of Vegetables. (M. E. Freeman.) This 

 study was undertaken to determine, if possible, the fate of certain constituents 

 of vegetables during cooking processes. Preliminary trials indicated that the 

 published analytical methods for determination of sugars, starch, pectic frac- 

 tions, and hemicelluloses do not, in all cases, allow direct application to the 

 material at hand. Modifications have been devised that allow the determina- 

 tion of pectic fractions in the presence of large amounts of starch. Extraction 

 periods may be shortened if samples are finely ground. In preliminary trials 

 ammonium oxalate seemed preferable to other agents for pectic extraction. 

 In the determination of pentoses by the steam distillation and bromine titration 

 method, the rubber connections in the steam line were found to cause error. 

 All glass apparatus is recommended. 



The Nutritive Value of Rare Elements in Plant Nutrition. (H. R. 



DeRose, W. S. Eisenmenger, and W. S. Ritchie. Cooperative with Agronomy.) 

 It is becoming more and more apparent that very small amounts of the so-called 

 rarer elements play an important part in the nutrition of plants. Because of 

 their peculiar ability to act as anions and cations, chromium and molybdenum 

 seemed to offer a fertile field for study. The latter had to be discarded and 

 zinc and copper were added to chromium because of certain connections to 

 other local projects. 



Tomato and buckwheat plants, both rapid growers, are being grown in sand 

 cultures with Knop's nutrient solution of Ca(N0 3 ) 2 , K 2 HP0 4 , MgS0 4 and 

 FeCl s to which are added dilute solutions of definite concentrations of the salts 

 of the metals in question. All salts used in the nutrient solution and in the 

 test solutions have been carefully recrystallized. The sand used has been 

 washed with acid, tap water, and distilled water and then dried at 100° C. to 

 insure the absence of interfering substances. The following concentrations are 

 being used: Copper .05, .15, .5, 1, 5 ppm; Zinc .05, .10, 10, 30 ppm. Concen- 

 trations of chromium will be used in the initial studies as follows: 1, 10, 20, 

 30, 40, 50, 60 ppm. 



This project has not been in operation long enough to justify the presenta- 

 tion of results. 



