16 



PRACTICE 7 



Determination of Flocculating Action of Lime. 



Take four bottles and in one put 200 cc. of distilled water, as a 

 check, in another 200 cc. of .1 percent solution of lime, in another 200 

 cc. .01 percent and in the fourth .001 percent solution. Add to each, 

 three grams of finely ground clay and shake for ten or fifteen minutes. 

 After shaking take out a drop from the check and .1 percent solution 

 and examine under a microscope with a high power. Then pour some 

 of the contents of the bottles into tubes and whirl in the centrifuge, 

 stopping every two or three minutes to note the effect upon the clear- 

 ness. Whirl for at least fifteen minutes. After centrifugation, pour 

 the contents of the tubes into their respective bottles, shake thor- 

 oughly and set aside, observing them occasionally to determine the 

 time required for complete sedimentation in each case. 



Make sketches of the appearance of the check and the 0.1 per- 

 cent solution under the microscope. 



Which is thrown down first by the centrifuge? Why? 



What practical application of this principle in farm practice? 



