140 SOIL PHYSICS AND MANAGEMENT 



9. What advantage does Hilgard'a method possess over Schone'sT 



10. What effect does whirling the sample in the centrifuge have? 



11. What is the principle of Voder's machine? 



12. What is the advantage of King's aspirator? 



13. Describe the method of King. 



14. What is the importance of colloids in soils? 



15. What are colloids? 



16. \Vhy may substances be in both colloidal and crystalloidal forms? 



17. Give examples of inorganic colloids. 



18. Give examples of organic colloids. 



19. Does colloidal condition depend upon physical condition or chemical 



composition ? 



20. What about the size of particles in colloids? 



21. Why do small particles remain in suspension so long? 



22. What is Brownian movement? 



23. What is dialysis? 



24. What difference in the dialysis between colloids and crystalloids? 



25. Discuss diffusion of crystalloids in comparison to colloids. 



26. W T hat effect do colloids have upon the freezing and l>oiling points of 



liquids? 



27. What is peculiar in the electrical behavior of colloids? 



28. What effect does an electrolyte have upon the colloids? 



29. When will an electrolyte completely precipitate clay in suspension? 



30. Wliat is adsorption? 



31. Is it uniform for all substances? 



32. What are the organic colloids in soils? 



33. W 7 hat are the mineral colloids? 



34. W r hat may be the mineral composition of clay ? 



35. What is tenacity? 



36. Define a " light " soil. A " heavy " one. 



37. What is the effect of moisture on tenacity? 



38. How may the tenacity of soils be diminished ? 



39. What causes soils to shrink? 



40. What benefit is derived by shrinkage? What disadvantage? 



41. Define plasticity. 



42. How may plasticity be increased? Diminished? 



43. What is the condition of a puddled soil ? 



44. What effect does water have on ease of puddling? 



45. Why does plowing tend to puddle a wet soil ? 



46. What agencies destroy a puddled condition? 



47. Why is fall plowing of heavy soils beneficial ? 



48. What advantages do silt soils possess over clays? 



49. What about shrinkage and granulation of silt soils? 



50. Why does sand possess little tenacity ? 



51. What effect does this have? 



52. What is " firing" of corn and what is the cause? 



53. What value has gravel in soils? 



54. What value have stones in soils? 



55. Define tenacity. 



56. Of what value are colloids in soils? 



57. What property causes black clay loam to '' roll " upon wagon wheels? 



