Improvements in the Treatment of Logwood Colouring Matter.
Year: 1898

page_text: PROVISIONAL SPECIFICATION.
Improvements in the Treatment of Logwood Colouring Matter.
We, JAMES EDWARD BEDFORD and CHARLES SAMUEL BEDFORD, both of 27,
Kirkstall Road, in the City of Leeds, Chemists, do hereby declare the nature of
this invention to be as follows:-
This invention has for its object the preparation of oxidised logwood extract
from fresh logwood by making use of the oxidising effect which nitrites possess
when heated with various compounds of a phenolic nature.
To illustrate this action:-10 kilos. haematoxylin are ground into a paste
with 20 litres water containing in solution 2 kilos. sodium nitrite. The mix-
ture is heated to 85° C. with constant stirring. The melt effervesces and gradu-
ally darkens in colour. After 3 hours heating the sodium haematein is produced,
a sample of the melt dissolving in water with a ruby tint.
On the large scale we add to the concentrated extract of fresh logwood the
requisite quantity of sodium nitrite dissolved in water & heat the mixture to 85° C.
with agitation till the reaction is complete.
The quantity of sodium nitrite necessary to convert the greater part of the
haematoxylin contained in the extract into haematein requires to be determined
by small trials but the following will illustrate the proportions required:-to
500 kilos. Honduras logwood extract at 45° Twaddle in a steam jacketted vessel
titted with an agitator we add 100 kilos. water containing in solution 22
sodium nitrite. The mixture is heated to 85° C. & stirred for 3 hours.
On cooling the haematein sodium salt seperates out as a pitchy mass.
kilos.
Improvements in the Treatment of Logwood Colouring Matter.
We, JAMES EDWARD BEDFORD and CHARLES SAMUEL BEDFORD, both of 27,
Kirkstall Road, in the City of Leeds, Chemists, do hereby declare the nature of
his invention and in what manner the same is to be performed, to be particularly
lescribed and ascertained in and by the following statement:-
This invention has for its object the preparation of oxidised logwood extract
from fresh logwood by making use of the oxidising effect which nitrites possess
when heated with various compounds of a phenolic nature.
To illustrate this action:-10 kilos. of haematoxylin are ground into a paste

page_text: with 20 litres water containing in solution 2½ kilos. sodium nitrite. The mix-
ture is heated to 85° C. with constant stirring. The melt effervesces and gradu-
ally darkens in colour. After 3 hrs. heating the sodium salt of haematein is
produced, a sample of the melt dissolving in water with a ruby tint.
In like manner the haematoxylin in fresh logwood may be oxidised to haema-
tein within the wood. The logwood is chipped and after being moistened with
15 to 20 per cent. of hot water it is allowed to stand in a heap about 1 metre high
for 4 or 5 days being turned over every day. The wood is then spread out to
cool and watered with a solution of sodium nitrite equal to from 02 to 03 % on
The
the weight of the logwood dissolved in 10 % (on the logwood) of cold water.
heap is repeatedly turned over in order to incorporate the materials and care is
taken that the temperature does not rise above 20° C., otherwise the product
though possessing good dyeing power will be dark in appearance.
The whole process should be completed in 7 to 8 days, the logwood is then
ready for use.
When treating extracts, we add to the concentrated extract of fresh logwood,
contained in a capacious iron vessel fitted with a steam coil or jacket and an
agitator a solution of the requisite quantity of sodium nitrite and gently heat
the mixture with constant stirring till the reaction is complete. The quantity
of sodium nitrite necessary to convert the greater part of the haematoxylin con-
tained in the extract into haematein requires to be determined by small trials but
the following will illustrate the proportions required:-
To 500 kilos. Honduras logwood extract sp. gr. 1215 contained in a steam
jacketted vessel fitted with an agitator we add 100 kilos. water containing in solu-
tion 4 kilos. of sodium nitrite and 10 kilos. sodium carbonate, the latter serves to
neutralise any free acid that may exist in the extract. The mixture is stirred
for 3 or 4 hours at the ordinary temperature and then gradually heated during
3 hours to 80° C. On cooling the haematein sodium salt separates out as a
pitchy mass, this may be dried to form solid extract by gentle heat in a vacuum
chamber.
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 of nitrites of the alkali metals and ammonium nitrite for the pur-
pose of oxidising haematoxylin to haematein.
2. The preparation of oxidised logwood extract by acting on ordinary logwood
extract with a nitrite in the manner described.
3. The preparation of hacmatein within the pores of the dyewood by treating
the chipped logwood with a nitrite in the manner described.
Dated this 22nd day of February 1899.
JAMES E. BEDFORD,
CHAS. S. BEDFORD.