Animal Charcoal. 167 
quantity of fresh burned charcoal may be cautiously added 
to its contents without overflowing it. 
In a freshly prepared condition animal charcoal is but a 
feeble ozonizer, not even bearing comparison with many 
other less important substances ; but the curious and re- 
markable property of its ozonizing power is its increase of 
capacity by constant use. This may be achieved by being in 
contact fora long time with water containing large quantities 
of soluble organic matter. The material after such treat- 
ment presents a different appearance to new charcoal, 
being of a dead grey cast, much lighter in colour than 
when new, and it is entirely free from any surface powder 
that always attends new charcoal, and renders the liquid 
black on washing. 
When investigating this property, it occurred to me that 
the same power existed equallyin botholdand new charcoal, 
but from the circumstance of new charcoal being invariably 
covered with a very fine powder, the pores on its surface 
were impaired; or that from this or other cause, it was pre- 
vented from absorbing the test liquid into its cells, and 
consequently calling a less area of surface into operation 
as an ozonizing agent. To ascertain the correctness of 
this view, I submitted equal quantities of new and old 
charcoal (by old, I mean such as had been used for several 
years as a filtering medium) to distilled water and spirits 
of wine alternately, for over a fortnight, taking precaution 
finally, to thoroughly wash both samples in water. They 
were then dried at ordinary temperature, and tested for 
their ozonizing capacity. The new I found to bear but 
very poor comparison with the old for ozonizing power. 
The next point of interest to ascertain was, as to which 
of the constituent elements composing the charcoal, the 
property owed its origin first. Neither phosphate of lime, 
carbonate of lime, nor carbon, whether in the form of wood, 
charcoal, graphite, or other state, is capable of ozonizing to 
any extent whatever, wood charcoal, however, taking slight 
exception to the rule. In substance, therefore, the consti- 
tuents are inert. Samples of good ozonizing animal char- 
coal, such as just described as old, wete treated as follows: 
—Ist, To incineration to expel the carbonaceous and vola- 
tile matter, leaving the phosphate of lime and earthy salts; 
2nd, By digestion with hydrochloric acid to abstract the 
calcigeneous phosphates and carbonates; and finally, 
another sample was pulverised as finely as possible in a 
pestle and mortar. On testing each residue, the results 
