24 MASS. EXPERIMENT STATION BULLETIN 398 



Chemical Changes in Cooking Quality of Vegetables. (Monroe E. Freeman.) 

 A quantitative method for measuring the texture of baked potato tissue by esti- 

 mating the pore space of dried slices was found to be satisfactory. The method 

 was applied to the study of texture changes in tubers during winter storage. 

 Samples stored at 35° and 50° F. for 76 days, 130 days, and 161 days were baked 

 and the texture was measured or estimated by three methods. Center rot and 

 "blackening" appeared in so many tubers that conclusive results were not ob- 

 tained. From the sound samples available, however, there seemed to be very 

 little change in specific gravity during the storage period. A visual scoring method 

 indicated that the cooking quality, i.e., texture, was lower in tubers stored for 

 longer periods and at the lower temperature. Toluene index of the tubers indi- 

 cated a small decrease in baking quality with time of storage at the higher temp- 

 erature, but because the samples were incomplete these results cannot be assessed 

 with any certainity. 



Physico-Chemical Properties of Starches. (Monroe E. Freeman.) The 

 anomolous heat capacities of starch-water systems reported in 1941 were care- 

 fully studied and applied to dextrin-water systems and to sand and water. The 

 data allowed a clear explanation of the phenomenon and its relation to the bound 

 water in lyophillic colloids and indicated the existence of a general phenomenon 

 of lyophillic systems that hitherto has not been clearly recognized. 



The Influence of Base Exchange Capacity and of Exchangeable Ions in Massa- 

 chusetts Soils on the Availability of Potassium. (Dale H. Sieling.) Pot cultures 

 of synthetic soil for plant growth were prepared by mixing quantities of a typical 

 tobacco soil, the Agawam fine sandy loam, with electrodialyzed bentonite which 

 had been adjusted to fixed calcium levels with calcium hydroxide. These cultures 

 were all of the same reaction and varied considerably in their base exchange ca- 

 pacity. Four levels of base exchange capacity, 7.1, 12.0, 17.0, and 22.0 milli- 

 equivalents per 100 grams, were established. At each base exchange capacity 

 level the soils were fertilized with four different quantities of potassium and with 

 a fixed quantity of both phosphorus and nitrogen. Nitrogen was also added at 

 various times during the growth of the plants. Each culture was prepared in 

 duplicate and contained 7000 grams of synthetic soil. Tobacco, Havana Seed 

 211, was used to test growth response and nutrient uptake. One plant was grown 

 in each culture and the soils were watered with distilled water whenever the rain- 

 fall was inadequate. 



Luxuriant growth was obtained in all cultures and there were no apparent 

 nutrient deficiencies or e.xcesses. Growth, as indicated by the dry weight of the 

 plants, was increased very little by addition of gypsum. The cultures having an 

 exchange capac't}' of 17.0 m<lli-equivalents gave plants of the highest average 

 weight. There was a tendency for the dry weight of plants to increase as the 

 quantity of potassium increased at each exchange capacity level. 



The Fixation of Arsenic in Soils and the Influence of Arsenic Compounds on 

 the Liberation of Fixed Phosphate. (Dale H. Sieling.) Ver\' marked differences 

 in sorption, of phosphate and arsenate were observed when ballmilled Kaolin 

 was used as the sorption substance. When 1-gram samples of ballmilled Kaolin 

 were shaken for two days with increasing quantities of sodium arsenate at pH 

 3.0 in 10 ml. of solution, there was a linear increase in the arsenate sorption up 

 to about 13.0 milli-equivalents per gram for a solution having 42.5 milli-equiva- 

 lents. At higher concentrations there was a sharp increase in the amount of 

 arsenate sorbed followed b>- progressively smaller increases in the pattern of a 

 typical adsorption. When 1-gram samples of Kaolin were shaken for seven days 

 with solutions of the same concentrations, instead of for two days, the sorption 



