Animal Charcoal. 169 
Substances capable of ozonizing, as a rule, may be arti- 
ficially produced by certain substances containing oxygen 
as an element, and capable of having such expelled by 
heat or other agency, without otherwise altering or destroy- 
ing their structural arrangement. In organic and other 
natural products, this property is also often met with to a 
considerable degree. 
Animal charcoal is of the class of substance in question 
—by depriving the organic substance in the process of 
burning of its combined oxygen, it becomes thus perma- 
nently ozonizable. This process of burning in practice is 
rarely, if ever, achieved in the first instance. Sugar-re- 
finers, and others using this charcoal, find that after the 
second or third burning the substance is considerably im- 
proved in its filtering power. Inthe use of animal char- 
coal, for filtering impure water, great caution is requisite in 
its proper selection and adaptation. If badly-burned char- 
coal be chosen, it will probably give rise to a numerous 
series of failures. A species of putrefaction of the un- 
charred organic remains is almost certain to set up in the 
locality of the defective parts, and soon, by spreading, con- 
taminate the whole of the charcoal, together with any sub- 
stance in contact with it. We find instances occur, that 
water, after having been in contact with this substance, be- 
comes actually less pure from the introduction of this 
extraneous matter. Such qualities of charcoal are actually 
useless for all practical application, and on the evidence of 
the tests before mentioned, should be scrupulously rejected. 
The treatment of animal charcoal by reburning, solely 
for this reason, is beneficial; for all others it is depreciatory 
to its virtue. The ozonizing capacity has been shown 
previously to exist in the combined substance, that each ele- 
mentary constituent was incapable of exercising this pro- 
perty, and hence we may reason, in proportion, that the 
balanced constituents are varied from their natural combi- 
nation, so would the ozonizing power be impoverished. 
Washing with dilute muriatic acid and reburning have been 
much used in the revivification of expended charcoal. The 
preference is now given almost exclusively in favour of the 
latter, but in practice they are both, after a certain time, 
incapable of effecting their purpose, and the charcoal be- 
comes useless. In theory, the failure is attributable to 
similar though opposite causes. By the treatment with the 
muriatic acid, the mechanically acquired matter that may 
be’ present on the surface of the charcoal, is loosened, and 
