Improvements in the Manufacture of Indigo-carmine from Phenyl-glycocoll and its Salts or Ethers.
Year: 1890

page_text: Date of Application, 17th Dec., 1890
Complete Specification Left, 17th Oct., 1991-Accepted, 28th Nov., 1891
HACIONAL DI BUIFICATION.
Improvements in the Manufacture of Indigo-carmine from
Phenyl-glycocoll and its Salts or Ethers.
I BENJAMIN WILLCOX, of 47 Lincoln's Inn Fields, in the County of Middlesex,
Patent Agent, do hereby declare the nature of this invention, which has been
communicated to me from abroad by Farbenfabriken vormals Friedrich Bayer
& Co., of Elberfeld, in the Empire of Germany, to be as follows:-
Several attempts have been made to convert phenyl-glycocoll, by means of
dehydrating agents, into indoxyl, or directly into the product of the oxidation of
the latter, or artificial indigo. The first satisfactory results obtained in this
direction are those described by Dr. Heumann in the Specification annexed to the
German Patent No. 54626.
Similar results have been obtained, in the same way, and almost at the same time,
by Biedermann and Lepetit (Berichte XXIII p. 3289). Heumann treated the
phenyl-glycocoll with caustic alkalies at a temperature of 260 to 350 degrees
Centigrade thereby obtaining indigo-white.
The employment of other condensing agents, such as chloride of zinc, and the
like, and concentrated sulphuric acid, afforded negative results (Berichte XIII
p. 3044).
No trace of indigo results when either ordinary sulphuric acid, or monohydratic
sulphuric acid, is employed but it is not so when sulphuric acid containing
anhydride is employed. Fuming sulphuric acid converts the phenyl-glycocoll,
with the greatest ease, into indigo, or rather directly into the sulpho-acid
thereof.
In the same way as in the manufacture of alizarine-bordeaux, by treating
alizarine with fuming sulphuric acid at a low temperature as described in the
Specification annexed to my application for Letters Patent No. 12715 dated
August 13th 1890, an oxidising action, with generation of sulphurous acid, takes
place. On simply treating phenyl-glycocoll with fuming sulphuric acid without
applying heat sulphurous acid is generated with a simultaneous formation of indigo-
carmine, the indoxyl sulpho-acid being probably formed in the first place and
afterwards oxidised into the indigo-carmine.
The following is given as an example shewing how this synthesis is accomplished
in practice.
One part of phenyl-glycocoll is dissolved in from about 2 to 3 parts of mono-
hydratic sulphuric acid and the solution is gradually poured at a temperature of
from, about 5 to 10 degrees Centigrade into 15 times the quantity of fuming
sulphuric acid containing about 70 per cent. of anhydride. The product of the
reaction, which is of a deep yellow colour, is poured into twice the quantity of
ulphuric acid, at 66 degrees Baumé, with precautions against rise of temperature.
It dissolves readily therein with a blue colour and the odour of sulphurous acid
becomes perceptible.
When the solution is diluted with ice it acquires the green-blue tone of an indigo-
armine solution and the colouring matter, or dyestuff, is readily precipitated there-
rom, in the usual form of flakes with a coppery lustre, by means of common salt.
The proportion of anhydride in the sulphuric acid, the quantity of the same, and
he temperatures employed, may vary within very wide limits but when fuming
ulphuric acid of low percentage, (say 20 per cent. for example,) is employed the
emperature of the reaction should be higher, or a longer time be allowed for the
reatment.

page_text: It is evident that the salts, and ethers, of phenyl glycocoll may be subjected to
similar treatment.
5.1
Dated this 16th day of December 1890.
J. H. JOHNSON & Co.,
47, Lincoln's Inn Fields, London, W.C., Agents.
COMPLETE SPECIFICATION.
Improvements in the Manufacture of Indigo-carmine from
Phenyl-glycocoll and its Salts or Ethers.
I, BENJAMIN WILLCOX, of 47 Lincoln's Inn Fields, in the County of Middlesex,
Patent Agent, do hereby declare the nature of this invention (which has been 1
communicated to me from abroad by The Farbenfabriken vormals Friedrich
Bayer and Company of Elberfeld in the Empire of Germany) and in what manner
the same is to be performed, to be particularly described, and ascertained, in, and by,
the following statement:-
I
Several attempts have been made to convert phenyl-glycocoll, by means of 1
dehydrating agents, into indoxyl, or into indigo, the product of the oxidation of
indoxyl. The first satisfactory results obtained in this direction were embodied
by Dr. Heumann in the Specification annexed to the German Patent No. 54626.
This chemist treated phenyl-glycocoll with caustic alkalies at a temperature of
260 to 350 degrees Centigrade, thereby obtaining indoxyl, or indigo-white, but he
was unable to effect the conversion by means of ordinary condensing agents, such
as chloride of zinc, and the like, or concentrated sulphuric acid, (Berichte der
Deutschen Chemischen Gesellschaft 1890 XXIII 3044). To obtain indigo-carmine
-from-the indoxyl produced as aforesaid it is necessary to oxidize the indoxyl, thus
-forming the so called insoluble indigo, and then-to-sulphonate this insoluble_indigo.
By thic present invention indigo-carmine is produced-from-phenyl-glycocoll at one
operation.
My foreign correspondents have discovered that on simply treating phenyl-
glycocoll with fuming sulphuric acid, (that is a mixture of sulphuric acid-and
sulphuric anhydride,) and subsequently removing the excess of anhydride in any of
the well understood ways appropriate to the purpose, indigo-carmine, (the disulpho-
acid of indigo,) is produced. In this case sulpho dioxide is evolved, oxidation
taking place as in-the-manufacture of alizarin-bordeaux from alizarin and fuming
sulphuric acid at a low temperature by the process described in the Specification-
of Letters Patent No. 12715, dated August 13th, 1890.
The process may be carried out in the following manner; but I do not limit
myself to the precise details which I give :-
part, by weight, of phenyl-glycocoll is thoroughly mixed with 20 parts, by
weight, of pure dry sand and the whole is introduced into 20 parts, by weight, of
fuming sulphuric acid containing 80 per cent. of anhydride; care being taken during
the whole operation that the temperature does not rise above about 30 degrees
Centigrade. A yellow liquid is thus obtained which yellow liquid is then diluted
with such a quantity of concentrated sulphuric acid, at about 60 degrees Beaumé,
as is necessary for the conversion of the sulphuric anhydride in excess into sulphuric
acid. There is thus obtained a liquid of an intense blue colour.
This blue liquid is then poured upon ice.; and the dye stuff may be directly
salted out in the usual manner with common salt. The dyestuff, thus obtained, is
pure indigo-carmine and can be employed in the same way, and for the same
purposes, as the indigo-carmine of commerce, but the shades obtained by the use of
the dyestuff produced as aforesaid are superior to those afforded by most samples
of commercial indigo-carmine.
The quantity of funning sulphuric acid and, the amount of anhydride therein and
the temperature employed may vary within wide limits.

page_text: The process of removing the anhydride is not restricted to the employment of
concentrated sulphuric acid but can be carried out also in the well understood other
ways appropriate to this purpose. When, for example, the mixture obtained by the
treatment of phenyl-glycocoll with fuming sulphuric acid is exposed to the air, or
when a current of moist air is led through the said mixture, indigo-carmine is likewise
formed, but its production proceeds slowly; that is to say, at a rate corresponding
with the conversion of the sulphuric anhydride into sulphuric acid by the gradual
attraction of water from the moist air.
Instead of phenyl-glycocoll its salts or ethers can also be employed for the
production of indigo-carmine by this process.
It is to be noticed that no trace of indigo, or of any product that can be easily
converted into indigo, or any product of indigo, is obtained when either ordinary
sulphuric acid, (oil of vitriol,) or the so-called monohydrated acid, is used.
Having now particularly described, and ascertained, the nature of the said inven-
tion, and the manner in which the same is to be performed, I declare that what
I claim is :-
1. In the manufacture of indigo-carmine the direct treatment of phenyl-glycocoll,
or its salts or ethers, with fuming sulphuric acid.
2. The manufacture of indigo-carmine by the direct treatment of phenyl-glycocoll,
or its salts or ethers, with fuming sulphuric acid, and the subsequent removal of
the sulphuric anhydride, present in excess, in any of the ways appropriate to the
purpose.
Dated this 10th day of October 1801
B. WILLCOX,
47, Lincoln's Inn Fields, London, W.C.