IMPROVEMENTS IN THE MANUFACTURE OF DECOLORIZING • AND PURIFYING CHARCOAL
Year: 1858

page_text: LETTERS PATENT to Hamilton Shirley Warner, of Trinidad, Gentleman,
for the Invention of "IMPROVEMENTS IN THE MANUFACTURE OF DECOLORIZING
• AND PURIFYING CHARCOAL."
Sealed the 14th December 1858, and dated the 15th June 1858.
PROVISIONAL SPECIFICATION left by the said Hamilton Shirley Warner
at the Office of the Commissioners of Patents, with his Petition, on the
15th June 1858.
I, HAMILTON SHIRLEY WARNER, of Trinidad, Gentleman, do hereby declare
the nature of the said Invention for "IMPROVEMENTS IN THE MANUFACTURE OP
DECOLORIZING AND PURIFYING CHARCOAL," to be as follows:-
My Invention consists of certain processes for the production of decolorizing
and purifying charcoal from the pitch or asphalte of the pitch lake of Trinidad.
In order to explain clearly the methods of operation which I adopt for this
purpose, it will be proper briefly to state the principle on which the manu-
facture depends.
It has been ascertained by the researches of several eminent chemists, that
the decolorizing and purifying powers of different charcoals depend entirely on
the carbonaceous matter in them, but that for such carbonaceous matter to act
efficiently it must not be of too compact a texture, in fact that the more

page_text: porous it is the more it acts on solutions brought into contact with it.
Animal charcoal consists of a porous or spongy mass of calcareous matter
(bone earth), through which is diffused a carbonaceous matter derived from
the gelatine of the bones from which it is made. The pitch of the pitch lake
at La Brea, in Trinidad, does not contain such substances as can efficiently act
the same part as the bone earth in animal charcoal; I therefore use it merely
as affording carbonaceous matter, and cause this carbonaceous matter to be
diffused or spread through a substance, which may perform the same function
as the bone earth in animal charcoal.
It is evident that for this purpose it is necessary to choose some substance
that is porous, that is not fusible by the heat employed to carbonize the pitch,
and that is not decomposed by such heat, or that, if decomposed, will not yield
any substance injurious to the liquids that may be filtered through it. I have
hitherto principally used clay, and also the porous stone or gravel of the hill of
San Fernando, in Trinidad, (which is, I believe, a silicate of alumina and
magnesia,) as most nearly fulfilling these requirements; but any other substance
possessing the above properties, such as pumicestone, broken brick, spent
animal charcoal, calcined bones, &c., would be suitable.
There are several modes by which from these materials decolorizing and
purifying charcoal can be made.
1. The pitch may be simply fused in a proper vessel, and when melted, the
clay, gravel, or other porous material may be added, it being in a dry state,
and, if necessary, previously crushed to reduce it to particles of a suitable size;
the heat is then raised and continued as long as any volatile matter is given
off by the pitch. at a red heat. During this operation the materials should be
kept stirred, as they are very bad conductors of heat. The stirring, however,
has the disadvantage of rubbing down a great deal of the charcoal into dust,
which has to be separated afterwards by sifting.
2. The pitch may be ground to powder and the clay or other porous
material reduced, by sifting or otherwise, to grains of the size the charcoal is
required to be. They are then mixed and burned, either by heating in small
iron pots, or by causing the mixed material to flow slowly through a pipe of
iron or earthenware, which is passed through a furnace in a vertical or inclined
position, and kept at a strong red heat. Instead of this, the mixed powders
may be fed into the upper end of a revolving cylinder, open at both ends, and
heated by a furnace, and mounted with its axis slightly inclined to the
horizon, so that the powder may gradually move along the cylinder as it
revolves, and at last fall out at the lower end burnt. Again, the carbonizing
may be effected by simply heating the mixed ingredients on an iron plate or

page_text: slab under which is a fire. Powdered pitch may also be mixed with spent
animal charcoal in reburning.
3. The pitch and clay may both be reduced to fine powder, mixed, then
slightly moistened with water, and granulated by appropriate machinery, which
may be constructed in any suitable manner. I do not claim any special
arrangement of machinery for the purpose. The grains are then to be dried
and burned in any of the ways above mentioned.
These different modes of proceeding may be considerably varied without
affecting the principle involved, which is that of diffusing the carbonaceous
matter derived from pitch through some porous or spongy substance not
injuriously affected by being heated in contact with pitch.