854 STATE BOARD OP AGRICULTURE. 



mass. This was tried and, true to the prediction, the bine litmus paper 

 did turn red. Tlio case then according to these series of experiments 

 stood as follows : A soil in the natural condition showed a very high 

 lime requirement according to the freezing point method, and gave an 

 absorption curve. When this soil was treated with an excess of acid, the 

 supernatant liquid was almost neutral both according to the freezing 

 point method and the litmus paper test, while the sediment or soil mass, 

 was acid to the litmus paper and gave an acid curve with the freezing 

 point method. When this sediment was washed with water the acid or 

 substance which yielded the acid curve and which was not equally repre- 

 sented in the supernatant liquid, disappeared. 



The above series of experiments were repeated a great number of times 

 using different soils, including some of the acid soils from the Rhode 

 Island Experiment Station plots, and various inorganic acids, with ex- 

 actly the same result. 



To many soils were added as much as 60 c. c. N/100 HCl to 10 grams 

 portions, without the supernatant liquid turning the blue litmus paper 

 red, at least not immediately. Many of these litmus paper tests were re- 

 peated and verified by Prof.A. J. Patten and Prof. M. M. McCool. 



After the foregoing series of experiments were completed there ap- 

 peared an article by Rice^ entitled ''Soil Studies." In this paper Rice 

 presents data on the basic exchange between soils and salt solutions as 

 measured by the hydrogen ion concentration method. In connection 

 with these studies he mentions a single experiment in which he shook 

 two soils, which responded strongly to all the usual tests for soil acidity, 

 with three times their quantity of N/100 HNO,. He found, according 

 to the hydrogen ion concentration method, that the strength of the 

 acid added had been considerably reduced after contact with the soil. 

 In conclusion he says : "Hence, even acid soils may neutralize acids to 

 some extent. Whether or not, in addition, some of the acid was adsorbed 

 by the soil was not determined." 



It may "be accepted then as an estadUsJied fad that when a soil, which 

 takes up a large amount of lime, is treated with an excess of acid, up 

 to a certain extent, the svpcniatant liquid ma.}) he neutral or only slightly 

 acid, while the soil mass itself is strongh/ acid to litmus paper and gives 

 an acid curve with the freezing point method. 



The interesting question now is, how may this phenomenon be ex- 

 plained? The q,uestion of neutralization of the supernatant liquid 

 could be dispensed with at once by assuming that the bases of the soil 

 neutralized the acid. But how about the acid remaining in the soil 

 itself? It must be immediately declared that no satisfactory explanation 

 can be offered at this time for the latter phenomenon. The problem is 

 under special investigation and it is hoped to discover the true explana- 

 tion. The following facts, however, should be recorded at this time: 



The acid which remains in the soil mass and causes an acid curve to 

 be obtained must be in solution, on two main grounds, (1) it can be re 

 moved very readily by washing with water and (2) it affects the freezing 

 point depression, since on being neutralized with Ca(0H)2 the depres- 

 sion of the soil is decreased, indicating that the acid combines with the 

 base to form an insoluble compound and thereby is removed from solu- 

 tion, or to form a soluble salt which has a lower degree of dissociation 



»J. Phy. Chem.. 20, 214, (1916). 



