Improvements in the Purification of Coal Tar, and Rendering same a Suitable Paint or Coating for Iron and Steel Structures.
Year: 1890

page_text: Date of Application, 15th July, 1890
Complete Specification Left. 10th Apr.. 1891-Accepted, 13th June. 1991.
PROVISIONAL SPECIFICATION.
Improvements in the Purification of Coal Tar, and Rendering same a
Suitable Paint or Coating for Iron and Steel Structures.
We, THOMAS HENRY DAVIS, Analyst, 27 Durham Road Manor Park Essex and
ARTHUR HENRY DAVIS Paint Manufacturer 45 King Street, Rock Ferry Cheshire
do hereby declare the nature of this invention to be as follows:-
Coal tar is washed by agitation with a solution of sulphate of copper, or sulphate
of zinc by which means sulphuretted hydrogen and ammonia are extracted from the
tar. After settling sufficiently long for separation, the tar is drawn off from the
bottom of the agitating vessel and is then subjected to repeated washings with
small quantities of clean water, until the washing water is quite neutral. The
washed tar is then run to a tank for final settling and after resting there for several
days it is ready for use.
1 T. 1000
THOMAS HENRY DAVIS.
ARTHUR HENRY DAVIS.
COMPLETE SPECIFICATION.
Improvements in the Purification of Coal Tar, and Rendering same a
Suitable Paint or Coating for Iron and Steel Structures.
We THOMAS HENRY DAVIS, Analyst 27 Durham Road Manor Park Essex and
ARTHUR HENRY DAVIS Paint Manufacturer 45 King Street Rock Ferry Cheshire
do hereby declare the nature of this invention and in what manner the same is
to be performed, to be particularly described and ascertained in and by the following
statement:-
Coal tar in the condition either as obtained from gas works or after being refined
is treated by vigorous agitation in a suitable vessel with an aqueous solution of sulphate
of copper or sulphate of zinc. The agitation must be kept up for two hours, and so
performed as to ensure every particle of the tar being washed by the solution. By
this means the whole of the ammonia and of the sulphuretted hydrogen whether free
or combined is abstracted from the tar the former forms with the sulphuric acid of the
salt used a sulphate of ammonia and the latter an insoluble sulphide of copper or
zinc the whole is now transferred to a wooden tank of sufficient dimensions to hold
the entire charge and to leave room for a further agitation. It is at once thoroughly
washed, preferably by mechanical means with warm water for about an hour, and
then allowed to stand for 24 hours, at the end of this time, the tar is drawn off*
from the bottom of the tank and subjected to a further similar washing process,
which must be repeatedly performed until the washing waters are perfectly neutral
to litmus paper or other test. When this is the case the washing is complete and
the tar is of the neutral character the process is designed to accomplish. It is now
left at rest for 24 hours, the tar is then run off from the bottom and transferred to
store tanks for final settling. It is left at rest in these tanks for at least a week and
is then to be drawn off again from the bottom in the condition ready for sale.
When this purified tar is required as an antifouling as well as a preservative
coating for the bottom of ships or other submerged structures carbolic or cresylic
acid, either crude or refined is thoroughly incorporated with it in such proportions
as the natures of the waters, in which the ship sails or in which the submerged
structures may be placed.

page_text: The wash waters from the second process are collected and allowed to settle and
the precipitated sulphide of copper or zinc is collected by filtration through fine
canvas or after washing on the filter is treated with sulphuric acid in a suitable
vessel, by which means the sulphate of copper or zinc is re-obtained for
further use.
Having now particularly described and ascertained the nature of our said inven-
tion & in what manner the same is to be performed, we declare that what we
claim is
A material which when applied to iron & steel will adhere strongly whether
exposed or submerged in water. It is also a preservative for iron & steel protecting
either from corrosion and prevents the growth of animal or vegetable life on such
structures when submerged in sea or fresh water.
Dated this Eighth day of Al 1801
ARTHUR HENRY DAVIS,
40, Old Hall Street, Liverpool, Agent.