^^5 



Table 27. — Acidity hy the litmus method. Samples taken from five fields on 

 Carrington loam. 



Marshall Silt Loam. All the samples on this type (Table 28) were 

 acid with the exception of the second and third foot-sections of Set T 

 from Field IT. 



Discussion. The reaction toward litmus shows the soils of the 

 two Carrington series on the Kansan to be more acid than those on the 

 Late Wisconsin, while with the Fars^o silt loam the opposite is true. 

 The samples of Marshall silt loam were practically all acid. 



3. Reaction as Determined by the Truog Method. 



The reaction of the two sets of samples from each field was also 

 tested by the Truog (30) method. This method is briefly as follows: 

 To 10 grams of soil are added 1 gram calcium chloride. 0.1 gm. zinc 

 sulfide and 100 c.c water. The mixture is thoroughly shaken, heated 

 to boiling and after boiling one minute a strip of lead acetate paper is 

 placed over the mouth of the flask and the boiling continued two min- 

 utes longer, when the paper is removed. If the soil is acid the paper 

 will be darkened on the under side in proportion to the degree of 

 acidity. 



The results obtained by this method are reported in tables 29 to 

 32, and since they so closely resemble those secured by the litmus 

 method need no further discussion. A comparison of the indications 

 obtained by the two methods is given below. 



