Year: 1887

page_text: Date of Application, 21st Apr., 1887
Complete Left, 14th Jan., 1888
Complete Accepted, 17th Feb., 1888
We, JAMES WEST KNIGHTS of Cambridge, Analyst and WILLIAM DENNISON GALL
of Little Shelford, Cambridgeshire, Tar Distiller, do hereby declare the nature of this
invention to be as follows:-
We take the carbolic oil (or middle oil) obtained from tar by distillation, or any
other oil or naphtha from which it is desired to extract carbolic acid and add lime
preferably stirring it in, in sufficient quantity to convert the carbolic acid it contains
into carbolate of lime.
We then agitate the oil with a hot solution of sulphate of soda which converts the
carbolate of limo into carbolate of soda, the lime being simultaneously converted into
sulphate of lime.
We now allow the mixture to settle, when an oily layer will be at the top, containing
a deposit of sulphate of lime, and a watery layer at the bottom containing carbolic
acid combined with soda.
The watery liquid containing carbolic acid is now drawn off and separated from
the oily liquid.
Sulphuric acid is added to the watery liquid until it is neutral or slightly acid,
carbolic acid then separates and rises to the top, from which it is drawn off leaving
the liquid which consists simply of a solution of sulphate of soda, ready to use for
another operation with a fresh quantity of oil.
The carbolic acid obtained by us is much more pure than that obtained by the
ordinary process and the cost of extraction is much less, as we use the solution of
sulphate of soda over and over again, and the only waste product is the sulphate of
lime that remains in the exhausted oil from which it can be removed by straining or
filtering.
The liquid from which the carbolic acid is removed may be noutralized or rendered
slightly alkaline with carbonate or caustic soda, and is boiled by steam or otherwise
for a fresh operation.
The exhausted oil left in the mixing apparatus may be run out and passed through

page_text: filter bags to remove the sulphate of lime it contains and it can then be used for any
purpose for which tar oils are applicable.
In the above process carbonate of soda can be used instead of sulphate of soda in
which case the carbolate of soda liquor must be decomposed with carbonic acid gas to
liberate the carbolic acid and reproduce the carbonate of soda solution for the next
operation.
Slaked lime (Ca 2 HO) can be used in place of burnt lime (Ca O) but to produco
the same effect a larger quantity must be taken, according to the well known laws of
chemistry.
Other alkaline earths can be used in place of lime, such as Barium Strontium or
Magnesium in conjunction with a soluble sulphate or carbonate in place of sulphate of
soda but not so conveniently and cheaply.
In the case of a greater or less quantity of carbolic acid being contained in the oil
operated upon more or less of the lime and sulphate of soda must be used but in the
same proportions and care must always be taken to have sulphate of soda in chemical
excess of the lime used, that is more than sufficient to convert all the lime into sulphate
of lime, otherwise carbolate of lime will remain in the mixture and prevent a ready
separation of the two liquids.
Other tar acids may be extracted in the same way.

page_text: Improvements in the Manufacture of Carbolic Acid and other
Tar Acids.
We, JAMES WEST KNIGHTS of Cambridge, Analyst and WILLIAM DENNISON GALL
of Little Shelford, Cambridgeshire, Tar Distiller, do hereby declare the nature of this
invention to be particularly described and ascertained in and by the following
statement:-
This invention relates to a new or improved process for the manufacture of carbolic
acid from the carbolic oil (or middle oil) obtained from tar by distillation or from any
other oil or naptha from which it is desired to extract carbolic acid.
The process consists essentially in employing sulphate of soda and limo instead
of caustic soda the cost of lime being considerably less than that of caustic soda
whereby the production of carbolic acid is cheapened and the acid itself improved
in quality as caustic soda has a great tendency to dissolve napthaline and neutral oils
which lime has not.
The yield is also greater as will be apparent when the process has been fully
explained.
Supposing the oil or naptha to be treated to contain 10 per cent of carbolic acid we
employ with every 100 gallons of such oil or naptha 50 pounds of lime (Ca 2 HO)
freshly slaked and sifted and 150 pounds of sulphate of soda or salt cake (Na 2 SO 4).
The sulphate of soda is dissolved in such a quantity of water that the solution shall
measure about 100 gallons and this is heated to from 160 degrees to 200 degrees F.
by injecting steam or by other means; the limo is then added to the solution
and the whole mixed with the oil in a suitable vessel and briskly agitated by ordinary
means for one and a half or two hours after which the mixture is allowed to rest for
two hours or thereabouts when it will settle in two layers the upper one consisting of
oil and the lower one of solution of carbolate of soda in water."
After settling, the bottom liquid is drawn off by means of a cock at the bottom
of the mixing vessel and passed through canvas or other filtering medium to
eliminate any particles of sulphate of lime that may bo present at this stage. After
the bottom liquid has been drawn off the remaining sludge consisting of sulphate
of lime mixed with tar oil and carbolate of soda solution is passed into the
filter and the filtered liquid is allowed to settle when the clear liquid at the
bottom is drawn off and added to the liquid first filtered after which the upper
layer of exhausted oil is drawn off through the filter and collected in a separato
vessel.
The carbolate of soda liquor obtained as above is now to be decomposed by adding
sulphuric acid gradually until the liquid will turn blue litmus paper red or until it is
completely neutralized which may be known by the liquid ceasing to turn milky by
any further addition of acid and by carbolic acid rising and collecting on the surface
as an oily layer. It is now allowed to rest until the carbolic acid has completely

page_text: settled on the top and the liquid has become cool when the layer of carbolic acid can
be removed by skimming or drawn off by means of a syphon or other means.
The liquid remaining after taking off the carbolic acid consists of a solution
of sulphate of soda containing a little free sulphuric acid which must be
neutralized by adding carbonate or caustic soda until the liquid no longer reddens
blue litmus.
This liquor can then be used in a fresh operation with the addition of a fresh
quantity of lime and tar oil in the same proportions as in the first operation and thus
any carbolic acid not obtained during one operation will be obtained in the next so
that the loss on a singlo process cannot accumulate.
The sulphate of soda can, as shown be used over and over again and the only
substances that are expended in the process are limo and sulphuric acid which form
sulphate of lime as a waste or bye-product. To this must be added the trifling quantity
of carbonate or caustic soda required to remove the acidity of the sulphate of soda
after each operation.
The sulphate of soda should always be in chemical excoss of the lime used in order
to ensure completo decomposition of the whole of the carbolato of limo which would
otherwise provent a ready separation of the liquids after mixing or would clog
the filter cloths. A considerable excess of sulphato of soda is not injurious to the
process.
If the carbolic oil contains a greator or less proportion of carbolic acid than 10 por
cent, more or less sulphate of soda and lime should be used the relative proportions
being maintained.
To compensate for any loss of sulphate of soda in the operations a little of that
substance may be added to the liquor from time to time to maintain the original
strength, that is 150 lbs in solution per 100 gallons of the liquor.
Instead of lime any alkaline earth may be used such as baryta or strontia. Also
instead of sulphate of soda sulphate of potash may be used.
The process is also applicable for the extraction of other tar-acids.
In making up tho solution of sulphate of soda or maintaining its strength crystal-
lized sulphate of soda obtained as a bye-product in the ordinary method of making
carbolic acid may be used but about double the quantity would be required in
consequence of the water of crystallization contained in it.
The filtering operations may be carried on by means of a filter press or a vacuum
filter but in small operations the latter is unnecessary. The ordinary plant may be
used and the manipulation is the same as that with which all carbolic acid makers are
familiar.
Having now particularly described and ascertained the nature of our said invention
and in what manner the same is to be performed, we declare that what we claim is :—
1. The use in the manufacture of carbolic acid and other tar-acids of limo and
sulphato of soda in manner and for the purpose substantially as described.
2. The use in the manufacture of carbolic and other tar-acids of an alkaline
carth and an alkaline sulphate in manner and for the purpose substantially as
described.
Dated this Thirteenth day of January 1888.