June IS. 191S Antagonism between Anions as Affecting Barley 209 



bad effects of sodium carbonate ("black" alkali) and also as a stimulant 

 to certain legumes which are grown for forage. As was demonstrated 

 by Hilgard (i, p. 457-458) in proposing the use of gypsum for the last- 

 named purpose, the following reversible reaction takes place, which 

 accounts for the beneficial effect of the gypsum for reasons too well 

 known to need repetition here. 



Na,CO, + CaSO^ = Na^SO^ + CaCO^ 



However, Hilgard also obser\-es (i, p. 458), "of course, gypsum is of 

 no benefit whatever on soils containing no 'black' alkali, but only 

 ('white') Glauber's and common salt." The finality of this expression 

 only emphasizes again what has been noted so often before — namely, 

 the danger that lurks in positive statements, at least in the inexact sci- 

 ences, no matter how certain their correctness may appear at the time. 

 In the light of the more recent information on antagonism between ions, 

 one would not subscribe to the statement just quoted. It was, indeed, 

 because of the rapidly accumulating data on antagonism between salts 

 that we were led to doubt the finality of Hilgard's statement and to 

 learn by direct experiment the facts in the case. 



Accordingly an experiment similar to those above described was 

 arranged, except that sodium sulphate was used in constant toxic quan- 

 tity of 0.4 per cent and calcium sulphate (CaS04) in varying quantities 

 to determine whether any interaction occurs between these salts which 

 proves of value to plant growth in such soils as those here described. 

 It will be remembered that we are dealing here with the same anion 

 but with different cations, one of the latter having a higher valence than 

 the others. The evidence of antagonism given above was obtained with 

 the same cation but with different anions. Other information respect- 

 ing the mode of arrangement of the experiment, as well as the results 

 thereof, is given in Table V. 



Table V not only shows the incorrectness of Hilgard's view but evi- 

 dences most emphatically that calcium sulphate is a very efficient sub- 

 stance for the purpose of preventing the toxicity of sodium sulphate. In 

 this series we have antagonism in the first crop as well as in the second, 

 a phenomenon only very dubiously noted in the foregoing antagonism 

 series. That the relatively large additions of calcium sulphate should 

 continue, like some of the smaller additions, to show an effect antagonis- 

 tic to sodium sulphate is not surprising, inasmuch as gypsum is a rela- 

 tively insoluble salt and would therefore not be expected to cause an 

 increased toxicity when added to another salt, as would be the case with 

 the more soluble salts above studied. Two facts are shown in Table V 

 which are very difficult to explain. One is the different point as regards 

 the concentration of salts at which the most marked antagonism occurs 

 in the two crops, and the other is the behavior of small amounts of gypsum 

 91007°— 15 2 



