68 THE PHYSICAL PROPERTIES OF SOILS 



THIRTEENTH EXERCISE 



THE FLOCCULATING EFFECT OF LIME 

 UPON CLAY SOILS 



The addition of lime to a clay soil produces floccula- 

 tion, or a grouping together of the fine soil grains into 

 granules, which act physically very much as single 

 soil grains. The effect is equivalent to increasing the 

 size of the soil grains and giving to the soil the prop- 

 erties of a much coarser textured material. Fine 

 grained, stiff, clay soils tend to become loose and 

 friable when flocculation is induced. 



Flocculation is best shown in a soil suspended in 

 water. Work up in a mortar two lo-gram samples of 

 clay soil and place one in each of two glass cylinders. 

 Fill two-thirds full of distilled water. Leave one 

 cylinder untreated, and to the other add 20 cc. of a 

 saturated solution of lime-water. Shake both for sev- 

 eral minutes and note the formation of floccules in the 

 tube containing lime. Examine some of the suspended 

 material from both cylinders under the microscope. 



How does lime aid in clearing the solution? What 

 other materials are effective in producing flocculation? 



Set the cylinders aside and note the time required 

 for each to become clear by settling. Discuss the effect 

 of lime upon the physical character of the soil in the 

 field. 



References: 



Burkett, "Soils," Chapter XL 

 King, ''The Soil," p. 30. 

 Hall, 'The Soil," pp. 38-40. 



