146 ANIMAL CARBON, OR BONEBLACK. 
from the air until it has cooled, or it may be quenched 
while hot by sprinkling it with water, taking care to add 
no more than is necessary for that purpose. 
Thorough defecation, according to the method already 
prescribed, is a valuable auxiliary to the action of this filter, 
and these operations may be regarded as inseparable and 
indispensable in this process. 
Although many other forms of carbon might be proposed 
as substitutes for this preparation of boneblack, none of 
them have been found at all equal to it, for attaining the 
desired results. 
