The Production of New Yellow Dyestuffs called Thioflavines.
Year: 1888

page_text: Date of Application, 16th Oct., 1888
Complete Specification Left. 10th July, 1889-Accepted. 10th Aug., 1889
PROVISIONAL SPECIFICATION..
The Production of New Yellow Dyestuffs called Thioflavines.
1, GEORGE PITT of Sutton in the County of Surrey, Gentleman (a communication
to me from abroad by Leopold Cassella & Co. of Frankfurt on Main, Germany, Manufac-
turing Chemist) do hereby declare the nature of this invention to be as follows:-
:-
It is known that paratoluidine heated with sulphur is transformed into bases which
contain sulphur (Dahl & Co.'s German Patent No. 35790). The nature of the product
formed is altered by the proportional quantity of sulphur employed (Dahl & Co's German
patent application D 3362). Whilst the so-called thioparatoluidine of Dahl & Co. is
soluble in spirit and may be obtained by crystallization, the product becomes insoluble in
spirit when the quantity of sulphur is increased. Almost the same reactions take place,
when instead of paratoluidine, xylidine is used; the thionated bases therefrom have
first been mentioned in my correspondents German patent application dated
October 3rd 1888.
The invention is founded on the following facts ascertained and discovered by my
correspondents.
1st. The thionated primary bases from paratoluidine and xylidine can be readily
transformed into tertiary bases by alkylating or benzylating the same.
2d. The products resulting from this process yield to water the salts of tertiary
bases which dye mordanted cotton a bright yellow shade.
3d. The remainder which is insoluble in water can be converted into sulpho acids
in the usual manner. The alkaline salts of the sulpho acids are soluble in water and
dye unmordanted cotton.in an alkaline bath.
4th. The sulpho acids of the basic dyestuffs mentioned above under No. 2 are
likewise valuable dyestuffs, they dye unmordanted cotton in alkaline, and animal fibres
in acidulated baths.
In order to produce the alkylated bases all the methods can be used, which are
generally known in chemistry as fit for this purpose, as for instance treating with
halogenes of alkyles with or without pressure or with an acid and an alcohol or with
an alcohol alone.
It is the same with the process of sulphonation, wherein sulphuric acid containing
more or less anhydrous acid or other sulphonating agents having a similar effect may
be employed.
In the following I describe how the invention may be put into practice :
Example I. In a close autoclave heat 24 kilos of the thionated base from paratoluidine
with 30 kilos of methylalcohol and 12 kilos muriatic acid (of 1.16 specific gravity)
during 10 to 12 hours up to 160-170° c. The autoclave will be found to be filled
with crystals of the chlorhydrate. When these crystals are boiled with water, a part
thereof--the quantity of which varies according to the nature of the primary base
employed-will be dissolved and after filtration is precipitated by addition of common salt.
Thus there is obtained a coloring matter of basic nature, which dyes cotton, mordanted
with tannin and tartar emetic a bright yellow.
Example II. Dissolve 25 kilos of dimethylated base, the salts of which are not
soluble in water, in 70 kilos of mono hydrated sulphuric acid, then add 10 to 12 kilos
of acid of Nordhausen containing about 60%, anhydrous acid; at a temperature of 70
to 80° c. the sulphonation is terminated. The smelt is poured into cold water whereby
the sulpho acid is precipitated; the same is then separated by filtration, dissolved in
an alkali and again precipitated by addition of common salt; thus is obtained, after
dessication a new dyestuff, which dyes cotton in alkaline bath a bright yellow.

page_text: Example III. In the place of muriatic acid in the first example use 13 kilos of
benzylchloride and heat only up to 120 to 150° (.
Example IV. Instead of using in example II. the dimethylated base, the chlorhydrate
of which is not soluble in water, use the base, the chlorhydrate of which is soluble in
water.
Instead of reacting upon the direct products of the thionation of paratoluidine and
xylidine the separated bases can also be acted upon. The part soluble in spirit, for
instance, yields principally the colors, the chlorhydrates of which are soluble in water
and act as basic dyestuffs.
Either of the bases, except those of which the salts are soluble in water, or the sodium
salts of the sulpho acids above described, if put in contact with alcohol cause a véry
characteristic yellow fluorescence of the alcohol.
Dated this 16th day of October 1888.
CARPMAEL & Co.,
Agents for the Applicant.
COMPLETE SPECIFICATION.
The Production of New Yellow Dyestuffs called Thioflavines.
I, GEORGE PITT, of Sutton, in the County of Surrey, Gentleman (a communication
to me from abroad by Leopold Cassella & Co., of Frankfurt on Main, Germany,
Manufacturing Chemists,) 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:-
It is known that paratoluidine heated with sulphur is transformed into bases which
contain sulphur (Dahl & Co.'s German Patent No. 35790). The nature of the product
formed is altered by the proportional quantity of sulphur employed (Dahl's German
patent application D. 3362). Whilst the so-called Thioparatoluidine is soluble in spirit
and may be obtained by crystallization, the product becomes almost insoluble in
spirit, if the quantity of sulphur is increased. Almost the same reactions take place,
latter if instead of paratoluidine Xylidine is used. The thionated base deriving from the
has first been mentioned in Leopold Cassella & Co.'s German patent application C. 2635
dated 18th July 1888. Instead of pure paratoluidine and xylidine also mixtures of
these bodies with other aromatic bases, such as aniline, orthotoluidine &c. can be used
with a similar result.
The invention is founded on the following facts ascertained and discovered by my
correspondents.
1. The thionated primary bases, mentioned above, can be easily transformed into
new bases by alkylating or benzylating.
2. The products resulting from this process yield to water the salts of these bases
which dye mordanted cotton a bright yellow shade.
3. The residue, which is insoluble in water can be converted into sulpho acids in the
usual manners.
The alkaline salts of the sulpho acids are soluble in water and dye unmordanted
cotton in an alkaline bath a bright yellow.
4. The sulpho acids of the above mentioned primary thionated bases can also be
transformed into alkylated bases or their sulpho-acids.
In order to produce my alkylated bases I can use all the methods, which are known
in chemistry as fit for this purpose, as for instance: treating the primary bases with
balogenes of alkyles with or without pressure, or with an acid and an alcohol, or
heating the salts of the primary bases with an alcohol alone.
The sulphonation of the bases can be performed by means of sulphuric acid contain-
ing more or less of anhydrous acid or with other sulphonating agents having a similar
effect.

page_text: In the following I describe how my invention may be carried out :
Example I. In a closed vessel I heat 24 Kos. of the thionated base from paratoluidine
with 30 Kos. of methylalcohol and 12 Kos. of muriatic acid (1·16 spec. gravity) during
10 to 12 hours up to a temperature of 160 to 170° C. The autoclave will be found to
be filled with crystals of chlorhydrate. If the product of the reaction is boiled with
water a part thereof-the quantity varies according to the nature of the thionated
primary base used-will be dissolved, and after filtration is precipitated by addition of
common salt.
Thus I obtain a coloring matter of basic nature, which dyes cotton, mordanted with
tannin and tartar emetic, a bright yellow. The coloring matters belonging to this
group I name Thioflavine T.
Example II. 25 Kos. of methylated base, the salts of which are almost insoluble in
water, I dissolve in 70 Kos. of monohydrated sulphuric acid, I then add 10 to 12 Kos. of
fuming sulphuric acid, containing about 60% of anhydrous acid, at a temperature of
70 to 80° C. the sulphonation is finished.
The smelt I pour into cold water whereby the sulpho-acid is precipitated, I separate
it by filtration, dissolve it in an alkali and then precipitate the salt of the sulpho-acid
by addition of common salt.
After desiccation I obtain my new dyestuff, which dyes unmordanted cotton in
alkaline bath a bright yellow. The coloring matters belonging to this group I name
Thioflavine S.
Example III. In the place of muriatic acid in the first example I can use 13 Kos.
of benzylchloride and first heat up to 120° C. then to 150-170° C.
Example 1V. 345 Kos. of sodium salt of the sulfo acid of thionated paratoluidine
are heated in an open or closed vessel with 24 Kos. of ethylbromide, 8-2 Kos. of
hydrate of sodium and 50 Kos. of alcohol up 100-110° C. during several hours.
The thus produced coloring matter is dissolved in water and precipitated by addition
of common salt. The product is from a technical point of view identical with the
product obtained by the second example.
.
Instead of using in the above described processes the crude products which are
directly obtained by thionating paratoluidine xylidine &c., I may also use the bases
separated with acids, alcohols or other extracting solvents.
The coloring matters which I name "Thioflavine T" are obtained in the form
of yellow crystalline powders, which are the salts of yellow basic compounds.
Alkalies or acetates precipitate the base from the aqueous solution of the salts.
The base is a yellow powder difficultly soluble in water, more easily soluble in
alcohol. The sulphate and the nitrate are less soluble in water than the chlorhydrate,
the tannate is scarcely soluble in water.
The coloring matters dye mordanted cotton a bright yellow, and are well suitable
for printing on cotton; they dye wool in neutral bath and silk in acidulated or
neutral bath producing especially on silk a yellow of very characteristic greenish
fluorescence.
The sulphonated coloring matters, which I name "Thioflavine S" are easily soluble
in water, difficultly soluble in alcohol, with an intensive greenish fluorescence.
Diluted acids precipitate the free sulpho-acids of the dyestuffs from their aqueous
solutions.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
1. In the production of dyestuffs, the process substantially as described, of alkyl-
ating or benzylalkylating the thionated primary bases obtained by heating sulphur with
para-toluidine, xylidine or mixtures of these bases with other aromatic amines.
2. In the production of dyestuffs the process substantially as described of
separating from each other the said alkylated or benzylalkylated thionated bases.

page_text: 3. In the production of dyestuffs, the sulphonation, substantially as described, of the
bases above mentioned, the salts of which are almost insoluble in water.
4. In the production of dyestuffs, the method, substantially as described of alkyl-
ating or benzylalkalating the sulpho-acids or sulphonates of the primary thiobases
mentioned above.
5. As new acticles of manufacture the yellow dyestuffs described above and called
Thioflavines T and Thioflavines S.
CARPMAEL & Co.,
Agents for the Applicant.