PUKIFICATION OF WATER FOR DRINKING PURPOSES 20] 



Finely Sifted and Sterilised Hard-wood Ash 

 The temperature in both cases was 11° C. 



Note. — The water, after agitation with the wood-ash, acquii-ed of course an alkalinfi reaction. 

 It would appear that this alkalinity, which was more especially marked in the lowest layers, acted 

 prejudicially upon the bacteria, inasmuch as in the first experiment there were very many fewer 

 I organisms loimd at the bottom of the flask containing the treated than the untreated water, 

 whilst in the second experiment, when less wood-ash was added arid the alkalinity was therefore 

 much less marked, the numbers at the bottom were not diminished, but greatly increased. The 

 results are obviously in neither experiment solely attributable to the mechanical effect produced 

 by sedimentation, but are complicated by the chemical effect of the soluble iugi-edients of the 

 -wood-ash. 



Lime 



Temperature at "which vessels were kept = 8° C. 



After 42 hours the water was perfectly clear. 



The Ume was not sterilised, but was slaked and mixed with water, the resulting milk of 

 lime being then added to the experimental vessel. The water became alkaline after the addition 

 of the lime, and whilst this alkalinity at the bottom of the vessel was very strong after a 

 time, in the middle and upper layers it decreased the longer the water remained standing. 



It is unfortunate that the author does not give any 

 particulars concerning the chemical composition of the 

 water operated upon. It is, however, pretty obvious, 

 ■from the strongly alkaline reaction of the water after 



