8 MASS. EXPERIMENT STATION BULLETIN 449 



in large excess, the fluoride caused the formation of the soluble hexa-fluo-alumi- 

 nate ion. Fluoride was effective in replacing chemically combined phosphate 

 and arsenate. The effectiveness increased progressively as the concentration 

 increased until it was complete when the ratio of fluoride to aluminum reached six. 



Organic anions were effective in replacing phosphate which had been chemically 

 combined with iron or aluminum. Citrates, gallates, iso-ascorbates, tartrates, 

 and mucates were particularly effective; while gluconates, hydroxybenzoates, 

 and salicylates were less effective, and amino acids were not effective at all. 

 Only those anions possessing the property of forming stable complexes with the 

 iron or aluminum were effective in replacing the phosphate with which these 

 metal ions were chemically combined. 



Purified lignin and humus replaced chemically combined phosphate from basic 

 iron phosphate. An increase in hydroxyl concentration also was effective in 

 replacing chemically combined phosphate; however, its effectiveness was less 

 than that of some of the organic anions. 



Practical applications of the findings are suggested as follows: 



1. An increase in the actively decomposing organic matter and in the pH 

 value of an acid soil would result in the release of fixed phosphate and aid in pre- 

 venting further phosphate fixation. 



2. Soluble fluorides might be employed to release fixed phosphates. This 

 would be practical in those areas where fluorides are known to be deficient in 

 soils and water supplies. This fluoride deficiency has been shown to be related 

 to a nutritional deficiency in both man and animals which results in the develop- 

 ment of poor tooth and bone structure. The use of fluoride would then have 

 the two-fold effect of releasing chemically combined phosphate and increasing 

 the fluoride content of the crops and the water supplies, 



3. Many soils are made unusable for shallow-rooted crops because of the use 

 of excessive quantities of arsenates to control insect pests. In these cases arsenates 

 are fixed in the topsoil in large quantities. To remove the arsenate from the 

 topsoil and to cause its transfer into the subsoil, one could treat the topsoil with 

 phosphates, fluorides, lime, or organic matter, or combinations of these materials. 

 Shallow-rooted crops could then be grown on the reclaimed soils after appropriate 

 fertilization. 



The Absorption of Chemical Elements by Food Plants. (Walter S. Eisenmenger 

 and Karol J. Kucinski in cooperation with C. Tyson Smith, Feed and Fertilizer 

 Control Laboratory'. ) The object of this project is to determine the factors 

 which influence the intake of elements in plants. The relative intake by plants 

 of calcium, magnesium, potassium, and sodium was studied when applied singly 

 and in pairs. Sulfates, phosphates, chlorides, bromides, and iodides were also 

 determined in tissues of plants grown on soils treated with these anions. 



Analysis of seedlings grown in the greenhouse showed that the addition of 

 copper lowered the movement of magnesium from the nutrient medium and the 

 seed to the aerial portion of the plant. When copper was applied to soil in field 

 plots, the magnesium intake by plants was not lowered. However, when copper 

 and calcium w^ere applied together in the field plots, the amount of calcium ab- 

 sorbed by the plants was appreciably higher than where the same amount of 

 copper and calcium was applied singly. 



In another phase of this study, where sodium fluoride was applied to the soil, 

 the fluorine content of the plants increased proportionately with the increasing 

 rate of sodium fluoride applications to the soil. 



