EFFICIENCY OF CHLORIDE OF LIME 237 



and 0.1 c.c. direct, and dilutions of 1-100, 1-10,000 and 

 1-1,000,000 (five plates for each medium). 



7. Make duplicate agar shakes also, with the raw river 

 water and with the same after the chloride of lime has been 

 added. 



8. Incubate all plates and shakes at 37 C. Observe 

 each at the end of twenty-four and forty-eight hours. 



9. Count the agar plates at forty-eight hours and record 

 the results. Count the gelatin plates before the colonies 

 are obscured by liquefiers. 



10. What types of organisms have been destroyed? 

 What types remain? Is this according to the results of 

 other investigators (see Hooker, p. 23). Would you feel 

 safe in drinking this water? 



11. Examine the sewage in a hanging drop and draw 

 the types of organisms present. Note which types pre- 

 dominate, also note their comparative size and motility. 



12. Make records of these to compare with the data on 

 cultural determinations. Are all of these types found by 

 the cultural methods? 



13. Chloride of lime is used for purifying drinking water 

 in the proportions of 5 to 25 pounds per million gallons of 

 water. What effect does chloride of lime have on organic 

 matter, discoloration, turbidity and swampy or other 

 smells in raw water? 



14. 35% available chlorine is necessary for efficient 

 sterilization. The available chlorine is merely an index of 

 the efficiency of the chloride of lime. Chloride of lime in 

 its industrial applications of bleaching, deodorizing or 

 disinfecting does not act by its chlorine but by its oxygen. 

 Its action is not chlorination but oxidation. (Hooker, 

 P- 7.) 



15. What is the maximum limit for the amount of 

 chloride of lime used in dosing drinking waters? What is 

 the amount used for treating water on shipboard? Why? 



What is the minimum length of contact allowed between 



