IMPROVEMENTS IN TREATING MINERAL AND OTHER OILS, AND IN RECOVERING SULPHURIC ACID THEREFROM
Year: 1871

page_text: LETTERS PATENT to Robert Carter Moffat and Alexander M'Laren,
both of Glasgow, in the County of Lanark, North Britain, Analytical
Chemists, for the Invention of “IMPROVEMENTS IN TREATING MINERAL
AND OTHER OILS, AND IN RECOVERING SULPHURIC ACID THEREFROM.”
Sealed the 20th February 1872, and dated the 22nd August 1871.
PROVISIONAL SPECIFICATION left by the said Robert Carter Moffat
and Alexander M'Laren at the Office of the Commissioners of
Patents, with their Petition, on the 22nd August 1871..
We, ROBERT CARTER MOFFAT and ALEXANDER MOLAREN, both of
Glasgow, in the County of Lanark, North Britain, Analytical Chemists,
do hereby declare the nature of the said Invention for "IMPROVEMENTS
IN TREATING MINERAL AND OTHER OILS, AND IN RECOVERING SULPHURIC ACID.
THEREFROE," to be as follows, that is to say :-
This Invention relates to the well known process of treating mineral
and other oils with sulphuric acid for the purpose of purification, and
its object is principally to effect the recovery of a larger proportion than

page_text: and the mixture is agitated during about twenty minutes. Tarry matter
then separates containing almost all the sulphuric acid added, and is
run off from below the oil and into a vessel lined with Icad.' The oil
is next treated with one measure per centum of a solution of caustic
soda of ordinary commercial strength as used by mineral oil refiners, and
after agitation for a short time the "soda tar" is allowed to settle, and
is then run off. The treating or refining of the oil is continued in the
ordinary way, that is to say, it is distilled as often as may be found
necessary, and between each distillation is treated with sulphuric acid
and with caustic soda in the manner herein-before described, excepting
that after each distillation the proportions of acid and of soda are
reduced. The proportions of acids used may be varied to suit oils of
different qualities or kinds.
In order to recover the sulphuric acid we add about an equal volume
of hot water of a temperature of about 100 degrees Fahrenheit to the
tarry matter separated from the oil by and along with the acid and agitate
the mixture for twenty minutes longer. The water dissolves most of the
acid and separates it from the tar and is drawn off from beneath the latter
into a shallow iron box or tank lined with lead. The tar is agitated
with a second quantity of water which separates a further quantity
of acid, and which is afterwards added to that first separated. The
dilute and impure acid separated in this way is concentrated by
evaporation by applying direct fire or other heat to the lead lined tank
until the boiling point of the liquid is raised to from 380 to 440 degrees
Fahrenheit. During the evaporation tar separates and is carefully
skimmed from the surface of the liquid as it collects. On the boiling
point reaching about 300 degrees we place a loosely fitting lead lined
cover on the tank to prevent escape of acid into the air. When the
boiling point has reached from 380 to 440 degrees, we draw the fire or
discontinue the heat and allow the liquid to become cold. We then
mix with the liquid twice its volume of water, and after thorough
agitation allow the mixture to become quite cold, this operation causing
the separation of much carbonaceous matter. The liquid is next filtered
by pouring it through strong canvas stretched over a shallow lead lined
vessel and the liquid passing through is again concentrated as before
until its boiling point reaches 380 to 440 degrees, the surface being
frequently skimmed to remove carbonaceous particles. The liquid or
acid is finally further concentrated in glass stills, as practised by makers

page_text: of sulphuric acid, until it attains a specific gravity of about 1.815. A
very little nitric acid is added during the concentration to remove any
brown color and to render the acid clear. The sulphuric acid treated
in this way is suitable for reuse, and is quite equal to new acid of the
same strength.
Having thus particularly described our said Invention, and the manner
of performing the same, we have to state that we do not restrict our-
selves to the precise details herein-before described, but that what we
believe to be novel and original, and claim as the Invention secured
to us by the herein-before in part recited Letters Patent is,―
1. The treating of mineral or other oils with hydrochloric acid prior
to the application of other purifying processes, as herein-before described.
2. The recovering of sulphuric acid from mineral or other oils
previously treated with hydrochloric acid by washing the tarry matter
with water and concentrating the dilute acid, as herein-before described.
In witness whereof, I, the said Robert Carter Moffat, on behalf
of myself and the said Alexander McLaren, have hereunto set
my hand and seal, this Nineteenth day of February, in the year
of our Lord One thousand eight hundred and seventy-two.
D
Witness,
EDMUND HUNT,
Patent Agent,
Glasgow.
R. CARTER MOFFAT. (L.s.)