Improvements in or connected with the Manufacture or Production of Colouring Matters.
Year: 1892

page_text: Date of Application, 15th Aug., 1892
Complete Specification Left, 12th May, 1893-Accepted, 5th Aug., 1893
PROVISIONAL SPECIFICATION.
[Communicated from abroad by FARBENFABRIKEN vormals FRIEDRICH BAYER
& Co., of Elberfeld, in the Empire of Germany.]
Improvements in or connected with the Manufacture or Production
of Colouring Matters.
I HENRY EDWARD NEWTON of The Office for Patents, 6 Bream's Buildings,
Chancery Lane in the County of London, Patent Agent, do hereby declare the
nature of this invention to be as follows:-
In the Specification of the application for Letters Patent No. 190624, dated
November 4th 1891 (for an invention communicated by my present correspondents),
a process is described for producing leuco sulpho acids, and converting the latter
into acid dye-stuffs "fast" against alkalies, which consists in the condensation
of dialkylmetasulfanilic acids and dialkylorthotoluidinemeta sulpho acids, viz.:
dimethylmetasulfanilic acid, diethylmetasulfanilic acid, dimethylorthotoluidine
meta sulpho acid, or diethylorthotoluidiuemeta sulpho acid, with tetraalkylised
diamido-benzhydrols, and in the further oxidation of the leuco sulpho acids thus
produced.
My foreign correspondents have now found that the dibenzyl derivatives of
metasulfanilic and orthotoluidine meta sulpho acid, and analogous sulpho acids, are
likewise capable of being condensed with tetraalkyldiamidobenzhydrols, leuco-
sulpho acids being formed, which yield, by further oxidation, dye-stuffs of
technical value, as the shades produced by them are also "fast" to the action of
alkalies.
The leuco sulpho acids thus obtained can also be converted by means of
sulphurising agents into polyleuco sulpho acids, which are oxidizable into new
dye-stuffs different from the last named."
In order to illustrate (I) the manufacture of these dibenzyl derivatives of
metasulfanilic acid, orthotoluidine metasulpho acid and analogues thereof;
(II), their condensation with tetraalkyl diamidobenzhydrols; (III), the conversion
of the so formed leuco sulpho acids into polyleuco sulpho acids; and (IV) the
oxidation of the latter to form new dye-stuffs, the following four examples are
given in the said order, the parts being by weight.
PRODUCTION OF DIBENZYLMETASULFANILIC ACID.
17 parts of metasulfanilic acid are mixed with 30 parts of benzylchloride, and a
solution of 10 parts of sodium hydroxide, in 100 parts of water. The mixture is
heated in a vessel provided with a reflux condenser, until the whole benzylchloride
has entered into reaction. After removing the oily by-products formed by the
decomposition of benzylchloride, the produced di-benzylmetasulfanilic acid is
perfectly precipitated by carefully neutralising the soda-lye; the precipitate is
filtered off, washed out, dried, and ground.
The dibenzylmetasulfanilic acid obtained in this manner forms a white powder
which dissolves in alkalies with moderate facility, but in diluted acids with
difficulty.
If the metasulfanilic acid of the foregoing example be replaced by an equivalent
quantity of the ortho-toluidine meta supho acid, (CH, NH,: SO,H=1:2:+),
or of xylidine sulpho acids, or analogous sulpho acids, containing some of the amido
group and sulpho group in meta-position, the corresponding dibenzylorthotoluidine

page_text: PROCESS FOR CONDENSING
DIBENZYLMETASUFANILIC
METHYLDIAMIDOBENZHYDROL.
ACID WITH TETRA-
35 parts of dibenzylmetasulfanilic acid are added to a solution of 27 parts of
tetramethyldiamidobenzhydrol, in 270 parts of acetic acid, containing 75 per cent.
of pure acid, and this mixture is heated by means of a water bath until the hydrol
employed is no longer distinguishable.
The resulting liquid is poured into water and neutralised by means of sodium
carbonate. The leuco sulpho-acid separates as a greyish blue precipitate, which,
after washing and drying, forms a greyish blue powder, soluble with difficulty in
alkalies, and in diluted mineral acids.
CONVERSION OF THE LEUCO SULPHO ACID OBTAINED AS DESCRIBED IN THE
PRECEDING SECOND EXAMPLE, INTO A POLYLEUCOSULPHO ACID.
The leuco sulpho acid, which results from the treatment described in the second
example, is introduced, on cooling, into about five times its weight of fuming
sulphuric acid, containing 20 per cent. of anhydride.
After some hours' standing, the liquid is saturated with lime, and after filtering
off the calcium sulphate, sodium carbonate is added to the filtrate, until the calcium
salt of the polyleucosulpho acid is converted into the sodium salt. The solution of
the latter, obtained after filtering off the calcium carbonate, is evaporated, and the
resulting concentrated solution can directly be employed for the further oxidising
process. The sodium salt of the said polyleucosulpho acid forms a powder soluble
with ease in water and diluted mineral acids.
OXIDATION OF THE POLYLEUCOSULPHO ACID OF THE PRECEDING THIRD
EXAMPLE.
The oxidation is effected in the usual manner by means of lead dioxide in
presence of acetic acid.
After precipitating the lead as lead sulphate, and filtering off the latter, the
solution of the formed dyestuff is evaporated. The colouring matter thus pro-
duced forms a brown powder, and dyes wool in acid baths a blue similar to that
of "cotton blue R." The shades obtained are extraordinarily
"fast "
against
alkalies.
The colouring matter obtaining by condensing the leuco mono sulpho acid of the
second example, with tetramethyldiamidobenzhydrol yields in general similar
shades, and only differs by its lower degree of solubility, from the product which
results by combining the leucopolysulpho acid with the hydrol, as described in
the last example. Similar properties are characteristic of the other dye stuffs
of these two series.
. In the preceding examples, only one method is described for producing
dibenzylmetasulfanilic acid, a leuco sulpho acid, a leuco polysulpho acid, & the
corresponding dyestuff. This part of the invention however is not limited to the
processes above mentioned, as the production of the said acids and dye stuff can be
varied. For example, instead of the benzylchloride employed in the first example,
the corresponding quantity of another benzylhalogen (e.g., benzylbromide) can be
used; the caustic soda can be replaced by an equivalent proportion of caustic potash

page_text: or other alkali acting in a similar manner; the isolation of the di-benzylmeta-
sulfanilic acid may also be effected in another way. The above proportions
likewise can vary within wide limits, etc. The methods above described for the
production of the leuco sulpho acid, leuco polysulpho acid, and dye stuff, are not
the only ways of obtaining these products and the analogues thereof. The isolation
of the leuco compounds and dye stuffs, as well as the conversion of the leuco
products into colouring matters by oxidation, can in general be effected by means
of the known methods for the production of analogous triphenylmethane leuco
compounds, and triphenylmethane dye stuffs. The tetramethyldiamidobenzhydrol
employed in the above third example can also be replaced by equivalent pro-
portions of tetraethyldiamidobenzhydrol, dimethyl,-diethyl, diamidobenzhydrol, .
dimethyldibenzyldiamidobenzhydrol, diethyldibenzyldiamidobenzhydrol, trimethyl-
monobenzyldiamidobenzhydrol, triethylmonobenzyldiamidobenzhydrol, dimethyl-
ethylbenzyldiamidobenzhydrol, diethylmethylbenzyldiamidobenzhydrol, or analo-
gous tetraalkyldiamidobenzhydrols, and instead of dibenzylmetasulfanilic acid, the
corresponding quantity of dibenzylorthotoluidine meta sulpho acid, dibenzylxylidine
sulpho acid, or other analogous acids, can be employed.
In this manner, the analogous leuco sulpho acids, leuco polysulpho acids, and
dye stuffs are obtained.
My foreign correspondents have further found that analogous dye-stuffs viz. :
derivatives of diphenylnaphthylmethane and triphenylmethane coloring matters
similar to the above, result by employing, instead of the dibenzylsulpho acids,
certain aniline toluidine, xylidine, cumidinesulpho acids, and analogous sulpho
acids, which are substituted in the amido group by naphthyl, and must therefore be
termed phenylnaphthylamine sulpho acid, tolylnaphthylamine sulpho acid, xylyl-
naphthylamine sulpho acid, and the like.
.
In the Specification of the application for Letters Patent No. 7337, dated
16th April 1892, phenylnaphthylamine, tolylnaphthylamine, and analogous sulpho
acids, are described by my foreign correspondents. These sulpho acids contain
the sulpho groups in the naphthalene nucleus, as they result by heating naphthyl-
amine sulpho acids with aniline, toluidine, xylidine, and the like.
Sulpho acids of phenylnaphthylamine and analogous secondary amines containing
the sulpho groups in the benzene nucleus, have not however hitherto become known..
Such sulpho acids are, however, of high value, as my foreign correspondents have
found, for the production of dye stuffs analogous to those described in the Specifi-
cation of the application for Letters Patent No. 19062", and my foreign
correspondents have first produced these sulpho acids by heating aniline, toluidine,
xylidine, cumidine sulpho acids, or analogous acids with alpha or beta naphthyl-,
amine, whilst the isomeric phenylnaphthylamine sulpho acids, tolylnaphthylamine,
sulpho acids, etc., are inversely obtained by heating alpha or beta naphthylamine
sulpho acids with aniline, toluidene, xylidine, or other primary amines.
In order to illustrate in general the method for producing these sulpho acids, the
following example is given:
:-
PRODUCTION OF ALPHANAPHTHYLPARASULFANILIC ACID.
Thoroughly dried parasulfanilic acid, and four times its weight of alpha
naphthylamine, are heated at from about 150 to 200 degrees centigrade, until the
mass, at first liquid, becomes of a thick consistency. Soda lye then is added, and
the mixture is boiled after adding water. The alpha naphthylamine in excess
separating, a solution of the sodium salt of the so formed alphanaphthylpara-
sulfanilic acid results. This solution is poured out, and the sodium salt of the new
acid is precipitated by means of common salt. By adding muriatic acid to the
above solution of the sodium salt, the free acid can directly be precipitated. The
alphanaphthylparasulfanilic acid separates in long flat needles, similar to those of
phtalic acid anhydride.

page_text: . In an analogous manner, metasulfanilic acid, disulfanilic acid, ortho- and
paratoluidine mono sulpho acid, ortho and paratoluidindisulpho acid, xylidine
sulpho acids, cumidine sulpho acid, and analogues thereof, are converted into the
corresponding alpha and beta naphthylamido-sulpho acids, viz., by heating the
former with alpha or beta naphthylamine, substantially as herein before described.
Of course the method described in the preceding example for the production
of these series of alpha- and betanaphthylamidosulpho acids can be varied.
Thus, the proportion of alphanaphthylamine employed can be augmented, and in
consequence thereof, the temperature may be somewhat lowered.
The sodium salts resulting can be isolated in another way; for example, by
evaporating their solutions after pouring off the same from the naphthylamine in
excess. The sodium salts can be converted into the free acids likewise by sulphuric
acid or other acids.
The alpha and betanaphthyl derivatives of metasulfanilic acid, disulfanilic acid,
ortho and paratoluidine monosulpho acid, ortho- and paratoluidine disulpho acid,
xylidine sulpho acids, cumidine sulpho acids, and analogues thereof, exhibit in
general the same properties as the alphanaphthylparasulfanilic acid obtained
according to the above example.
It is known that the leuco products obtained from alkylated diamidobenzhydrols
and secondary amines, are oxidised to form dye stuffs only with difficulty; the
yields are small, and the dye stuffs thus resulting produce for the most part dull
shades.
In the Specification of the application for Letters Patent No. 19062ª, dated
November 4th 1891, a process is described by my foreign correspondents of
effecting the oxidation easily, viz., by substituting some of the nitroso group for
the hydrogen atom in the imido group of the leuco products, oxidising the nitroso
amines into dye stuffs likewise containing the nitroso amine group, and subsequently
separating the nitroso group.
My foreign correspondents have now found that the leuco products obtained by
condensing alkylated diamidobenzhydrols and the aforesaid phenylnaphthylamine,
tolylnaphthylamine, xylylnaphthylamine sulpho acids, and analogues thereof
containing the sulpho groups in the benzene nucleus, can be oxidised very readily,
and without employing intermediate nitroso amines, to form blue dye stuffs, the
shades of which are of great purity, whilst the isomeric sulpho acids containing
the sulpho groups in the phenyl nucleus, are not capable of being employed in this
process with good result."
The above mentioned acids, which result by heating meta- or para sulfanilic acid,
disulfanilic acid, ortho or paratoluidine monosulpho acid, ortho or paratoluidine
disulpho acid, xylidine sulpho acid, cumidine sulpho acid, and analogous amido
sulpho acids, with alpha or beta naphthylamine, and which are termed
naphthylaniline, naphthyltoluidine, naphthylxylidine, naphthylcumidine sulpho
acids etc., yield satisfactorily dye stuffs of the diphenylmethane series. The high
technical value of these colouring matters consists in their capability of producing
shades which are "fast" to the action of alkalies.
The following example is given in order to illustrate the method for producing
these new dye stuffs.
COLOURING-MATTER FROM ALPHANAPHTHYLPARASULFANILIC ACID AND
TETRAMETHYLDIAMIDOBENZHYDROL.
Equimolecular proportions of alphanaphthylparasulfanilic acid and tetramethyl-
diamidobenzhydrol, are heated in acetic acid solution by means of a water
bath. After a short time (say, about a quarter of an hour or half an hour),
the hydrol has perfectly entered into reaction. The so-formed mixture is poured
into water and rendered moderately alkaline by the addition of soda lye. In this

page_text: manner, the sodium salt of the leuco sulpho acid is precipitated in brilliant white
lamine, which dissolve with difficulty in cold water, but can easily be converted
into crystals by boiling water.
In order to convert the leuco sulpho acid thus obtained into the dye stuff, its
sodium salt is dissolved in strong acetic acid, and the oxidation is effected in the
usual manner, by means of the calculated quantity of lead dioxide.
•
The separated dye stuff is filtered off, dissolved in dilute sulphuric acid, and
after filtering the solution in order to remove the lead sulphate precipitated, the
dye stuff is salted out by means of common salt.
It produces on wool, in moderately acid baths, pure blue shades.
By replacing the alphanaphthylparasulfanilic acid by the isomeric betanaphthyl-
parasulfanilic acid, alphanaphthyl- or betanaphthylmetasulfanilic acid, or by
the equivalent proportions of alphanaphthyl- or betanaphthyldisulfanilic acid,
alphanaphthylorthotoluidine or betanaphthylorthotoluidine mono or disulpho
acid, alphanaphthylparatoluidine mono or disulpho acid, or by the alpha or beta
naphthyl derivatives of xylidine sulpho acids, cumidine sulpho acids, or analogues
thereof, the other dye stuffs derived from tetramethyldiamidobenzhydrol are
obtained. If the latter be replaced by one of the other above mentioned or
analogous tetraalkyldiamidobenzhydrols, and the aforesaid alpha or beta naphthyl
derivatives be employed, as second components, the other new dye stuffs are
obtained in the manner substantially as described in the preceding example.
The latter illustrates merely one method of producing one leuco sulpho acid
amongst many, and for oxidising this sulpho acid to form colouring matter. Of
course, the production of the said leuco sulpho acids and dye stuffs is not restricted
to the above particulars; for example, the condensation of the alkylated hydrols
with the different sulpho acids can also be effected in presence of other solvents
or diluents, and at temperatures somewhat higher or lower; the isolation of the
leuco sulpho acids and their conversion into dyestuffs can be carried out in general
by the methods known for producing analogous leuco sulpho acids and colouring
matters of the triphenylmethane or diphenyl naphthylmethane series.
The dye stuffs formed by condensing tetraalkyldiamidobenzhydrols with the
alpha or beta naphthylamide sulpho acids containing the sulpho groups in the
benzene nucleus, are of high technical value, as they are obtainable in a simple
manner, and yield on wool, in acid baths, blue shades distinguishable for their
purity and "fastness" against alkalies.
Dated this 15th day of August 1892.
NEWTON & SON,
Agents for the Application.
COMPLETE SPECIFICATION.
Improvements in or connected with the Manufacture or Production
of Colouring Matters.
I HENRY EDWARD NEWTON of The Office for Patents, 6 Bream's Buildings,
Chancery Lane in the County of London, Patent Agent, 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 :—
In the Specification of the Letters Patent No. 19062, dated November 4th 1891
(for an invention communicated by my foreign correspondents), a process is
described of producing leuco sulpho acids, and of converting the same into acid
dye-stuffs capable of withstanding alkalies, which process consists in condensing
tetraalkylised diamidobenzhydrols with dialkylineta sulfanilic acids and dialkyl
orthotoluidine metasulpho acids (viz., dimethylmeta sulfanilic acid, diethylmeta-
sulfanilic acid, dimethylorthotoluidinemetasulpho acid, or diethylorthotoluidine-
metasulpho acid, dibenzyl aniline disulpho acid, dibenzylorthotoluidinedisulpho
acid), and then oxidising the leuco sulpho acids thus produced.

page_text: My foreign correspondents have now found that the dibenzyl derivatives of
metasulfanilic and orthotoluidine metasulpho acid and analogous mono sulpho
acids, are also capable of being condensed with tetraalkyldiamidobenzhydrols,
leuco sulpho acids being formed which, on further oxidation, yield dye stuffs
of technical value, as the shades produced by them also withstand the action
of alkalies.
The leuco sulpho acids thus obtained can also be converted, by means of
sulphonating agents, into leucopoly sulpho acids, which are convertible by oxidation
into new dye-stuffs different from the last named.
In order to illustrate (I) the manufacture of these dibenzyl derivatives of
metasulfanilic acid, orthotoluidine metasulpho acid, and analogues thereof;
(II) their condensation with tetra alkyldiamido benzhydrols; (III) the
conversion of the leuco sulpho acids so formed into leucopoly sulpho acids; and
(IV) the oxidation of the latter to form new dye stuffs, the following four examples
are given, the parts being by weight:
:-
PRODUCTION OF DIBENZYLMETASULFANILIC ACID.
17 parts of metasulfanilic acid are mixed with 30 parts of benzylchloride and a
solution of 10 parts of sodium hydroxide in 100 parts of water. The mixture is
heated in a vessel provided with a reflux condenser, until the whole of the benzyl-
chloride has been acted on. After removing the oily by-products formed by the
decomposition of benzylchloride, the resulting dibenzylmetasulfanilic acid (dibenzyl
aniline meta sulpho acid) is completely precipitated by carefully neutralising the
soda lye; the precipitate is filtered off, washed, dried, and ground.
The dibenzylmetasulfanilic acid is obtained in this manner in the form of a
white powder, which dissolves with moderate facility in alkalies, but with difficulty
in diluted acids.
If, instead of the meta sulfanilic acid of the foregoing example, an equivalent
quantity of the orthotoluidine meta sulpho acid (CH, NH, SO,H=1: 2: 4),
or analogous sulpho acids (containing the amido group in meta position to the
sulpho group), be taken, the corresponding dibenzylorthotoluidinemetasulpho acid
and the analogous dibenzylamidometa monosulpho acids are obtained.
PROCESS FOR CONDENSING DIBENZYLMETA SULFANILIC ACID WITH
TETRAMETHYLDIAMIDO BENZHYDROL.
3
35 parts of dibenzylmetasulfanilic acid are added to a solution of 27 parts of
tetramethyldiamidobenzhydrol in 270 parts of acetic acid containing 75 per cent. of
pure acid), and this mixture is heated by means of a water bath, until the hydrol is
no longer distinguishable. The resulting liquid is poured into water, and
neutralised by means of sodium carbonate. The leuco sulpho acid separates as a 4
greyish-blue precipitate, which, after washing and drying, forms a greyish-blue
powder, which dissolves with difficulty in alkalies and in diluted mineral acids.
CONVERSION OF THE LEUCO SULPHO ACID OBTAINED AS DESCRIBED IN THE
PRECEDING SECOND EXAMPLE, INTO A LEUCOPOLY SULPHO ACID.
The leuco sulpho acid prepared in the manner described in the second example,
is introduced into about five times its weight of cold fuming sulphuric acid
(containing 20 per cent. of anhydride). After some hours, the diluted liquid is
saturated with lime, and after filtering off the calcium sulphate, sodium carbonate
4

page_text: FOURTH EXAMPLE.
OXIDATION OF THE LEUCOPOLY SULPIIO ACID OF THE PRECEDING THIRD
EXAMPLE.
The oxidation is effected, in the usual manner, by means of lead dioxide in
presence of acetic acid. After precipitating the lead, as lead sulphate, and
filtering off the latter, the solution of the resulting dye stuff is evaporated. The
coloring matter thus produced forms a brown powder, and dyes wool, in acid baths,
a blue similar to that of "cotton blue R." The shades obtained are extraordinarily
"fast" in presence of alkalies.
The coloring matter obtained in like manner from the leuco monosulpho acid of
the second example, yields, in general, similar shades, and only differs by its lower
degree of solubility from the product obtained from the leucopoly sulpho acid, as
described in the last example. Similar properties are characteristic of the other
dye stuffs of these two series.
In the preceding examples, only one method is described of producing dibenzyl-
metasulfanilic acid, a leuco sulpho acid, a leuco polysulpho acid, and the corre-
sponding dye stuff.
The present invention, however, is not restricted to the processes described in
the above examples, as these processes can be varied. For example, instead of the
benzylchloride employed in the first example, the corresponding quantity of another
benzylhaloid (e.g., benzylbromide) can be used, and instead of caustic soda, an
equivalent proportion of caustic potash, or another alkali acting in a similar
manner, can be used; the isolation of the dibenzylmetasulfanilic acid may also be
effected in another way. The proportions can also be varied within certain limits.
The above described methods of producing the leuco sulpho acids, leuco poly-
sulpho acids, and dye stuffs, are also not the only ways of obtaining these and the
analogous sulpho acids and dye stuffs. The isolation of the leuco compounds and
dye stuffs, as well as the conversion of the leuco products into coloring matters by
oxidation, can in general be effected by means of the known methods of producing
analogous triphenylmethaneleuco compounds and triphenylmethane dye-stuffs.
Instead of the tetramethyldiamido benzhydrol employed in the above third
example, equivalent proportions of tetraethyldiamidobenzhydrol, dimethydiethyl
diamidobenzhydrol, dimethyldibenzyl-diamidobenzhydrol, diethyldibenzyl diamido-
benzhydrol, trimethylmonobenzyldiamidobenzhydrol, triethylmonobenzyldiamido-
benzhydrol, dimethylethylbenzyldiamidobenzhydrol, diethylmethylbenzyldiamido-
benzhydrol, may be used; and instead of dibenzylmetasulfanilic acid, the corre-
sponding quantity of dibenzylorthotoluidinemetasulpho acid, dibenzylxylidine sulpho
acid, or other analogous acids, can be employed. In this manner, analogous leuco
sulpho acids, leuco polysulpho acids, and dye-stuffs, are obtained.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, as communicated to me from
abroad, I declare that what I claim is :-
1. The process of producing dibenzylamidometamonosulpho acids of the benzene
series (such as dibenzylaniline metasulpho acid, dibenzylorthotoluidinemetasulpho
acid, or the like) by heating meta amidosulpho acids of the benzene series (such as
aniline meta sulpho acid, orthotoluidinemetasulpho acid, or the like) with benzyl-
chloride, or other benzylating agents, in the presence of diluted alkalies.
2. The process of obtaining leuco compounds (leuco sulpho acids) belonging to

page_text: the triphenylmethane series, by the action of dibenzylamidometamonosulpho acids
(such as dibenzylanilinemetasulpho acid, dibenzyl orthotoluidine meta sulpho acid,
or the like) on the following alkylised diamidobenzhydrols:-
tetramethyldiamidobenzhydrol,
tetraethyldiamidobenzhydrol,
dimethyldiethyldiamidobenzhydrol,
dimethyldibenzyldiamidobenzhydrol,
diethyldibenzyldiamidobenzhydrol,
trimethylmonobenzyldiamidobenzhydrol,
triethylmonobenzyldiamidobenzhydrol,
dimethylethylbenzyldiamidobenzhydrol, or
diethylmethylbenzyldiamidobenzhydrol.
3. The process of transforming the leuco sulpho acids obtained as described in
the preceding second claim into the corresponding leuco poly sulpho acids, by
treating them with fuming sulphuric acid, or other agent producing the same or a
similar result.
4. The conversion of the leuco sulpho acids obtained as described in the preceding
second claim, and the transformation of the leuco poly sulpho acids obtained as
described in the preceding third claim, into the corresponding dye-stuffs, by
.oxidation.
5. As new manufactures: -
(a) the new dibenzylamidometamonosulpho acids (such as dibenzylanilinemeta-
sulpho acid, dibenzylorthotoluidinemetasulpho acid, or the like):
(b) the new leuco sulpho acids, leuco poly sulpho acids, and dye stuffs,―
obtained by means of the processes hereinbefore defined, or by any other process
producing the same result.
Dated this 12th day of May 1893.
NEWTON & SON,
Agents for the Applicant.