8 4 
HOUSEHOLD BACTERIOLOGY 
Purifying 
Water 
Filters 
Porcelain 
Filters 
supply which receives any house drainage or that from 
manured fields is in danger of contamination at any 
time. 
Impure water may be purified from all germs by 
boiling for half an hour. Such water, having lost 
the air which was dissolved in it, tastes insipid. The 
air may be restored by pouring the water a few times 
from one clean vessel into another, and this should be 
done in a clean place, that is, where there is little fly¬ 
ing dust. 
Most filters simply strain out visible suspended mat¬ 
ter or invisible but comparatively large animal or veg¬ 
etable forms. A flannel bag will do this, and it can 
and should be cleaned daily. It clears currant jelly, 
why not water? When charcoal forms a part or the 
whole of the straining medium, more organic matter 
is removed and therefore more color is taken out, but 
the charcoal soon loses its purifying power and must 
be cleaned or renewed. None of the ordinary faucet 
filters will remove the minute disease germs and there¬ 
by make a polluted water safe for drinking. Germ 
removal requires a very fine medium, which means 
slow straining. Certain filters, made of very fine un¬ 
glazed clay or similar substance, take out the germs 
themselves, but cannot remove the products of their 
life processes, which are soluble. In some cases these 
are as dangerous as the germ plant itself. If a filter 
does strain out the bacteria, then it is evident that 
the straining medium will become foul with them and 
