The Manufacture and Production of Indigo in a Form readily Soluble in the Vat.
Year: 1899

page_text: Date of Application, 20th Nov., 1899
Complete Specification Left, 16th Aug., 1900-Accepted, 22nd Sept., 1900
PROVISIONAL SPECIFICATION.
The Manufacture and Production of Indigo in a Form readily
Soluble in the Vat.
I, JAMES YATE JOHNSON, of 47, Lincoln's Inn Fields, in the County of London,
Gentleman, do hereby declare the nature of this invention (which has been
communicated to me by the Badische Anilin & Soda Fabrik, of Ludwigshafen-
on-Rhine, in the German Empire) to be as follows:-
It is well known that dry vegetable indigo in the form in which it is usually
put upon the market must be ground in specially constructed mills in order to
bring it to a condition in which it will readily and completely dissolve in the
indigo-vat. This grinding operation is frequently prolonged for days.
Synthetic indigo also, under some conditions, separates out in the last stage
of its manufacture in a crystalline condition and the crystals may be of such a
size as to injuriously affect the ready solubility of the indigo in the melt.
My foreign correspondents have discovered that indigo which is with difficulty
soluble in the vat, irrespective of its origin, can, by a simple treatment, be con-
verted into a new form of indigo which can be readily dissolved.
The new process, according to this invention, consists in treating indigo with
sulphuric acid under such conditions of concentration that no sulphonation of
the indigo takes place, whilst a sulphate of indigo, or loose combination of
sulphuric acid therewith, is formed. For this purpose sulphuric acid containing
about 65 to 85 per cent. H, SO, can be employed. The sulphate so obtained
crystallises in the form of black-brown needles. This body is collected and treated
with water, when it decomposes, and the regenerated indigo separates out in a
physical condition that is fitted for use in all kinds of vats, it being easily soluble,
even in the fermentation vat which acts particularly mildly. The new readily
soluble product is chemically indigo, but its physical condition is changed by
the treatment, and the change consists probably not merely in fineness of division
but in an essentially different molecular structure.
The following example will serve to further illustrate the nature of the inven-
tion but the invention is not confined to the example.
EXAMPLE.
Stir about one hundred parts of dry indigo, in the form of powder, into about
five hundred parts of sulphuric acid containing 75 per cent. H₂SO. Warm the
mixture, whilst carefully stirring, to about thirty degrees Centigrade. When
the mixture is effected so that a uniform paste is obtained allow the mass to stand
for about an hour. The sulphate of indigo is then formed. To obtain the
indigo in the aforesaid new physical condition, add to the entire mass about
two thousand parts of water. Stir well, collect the new indigo by filtration,
and wash until free from acid. The new indigo retains its valuable property of
ready solubility in the vat even after drying.
1000

page_text: The Manufacture and Production of Indigo in a Form readily
Soluble in the Vat.
I, JAMES YATE JOHNSON, of 47, Lincoln's Inn Fields, in the County of London,
Gentleman, do hereby declare the nature of this invention (which has been
communicated to me from abroad by the Badische Anilin & Soda Fabrik, of Lud-
wigshafen-on-Rhine, in the German Empire) and in what manner the same is
to be performed to be particularly described and ascertained in and by the follow-
ing statement:-
-
It is well known that dry vegetable indigo in the form in which it is usually
put upon the market must be ground in specially constructed mills in order to
bring it to a condition in which it will readily and completely dissolve in the
indigo vat. This grinding operation is frequently prolonged for days.
Synthetic indigo also, under some conditions separates out in the last stage
of its manufacture in a crystalline condition and the crystals may be of such a
size as to injuriously affect the ready solubility of the indigo in the vat.
.
My foreign correspondents have discovered that indigo which is with difficulty
soluble in the vat, irrespective of its origin, can by a simple treatment, be con-
verted into a new form of indigo which can be readily dissolved.
The process, according to this invention, consists in treating indigo with
sulphuric acid under such conditions of concentration that no sulphonation of
the indigo takes place, whilst a sulphate of indigo, or loose combination of
sulphuric acid therewith, is formed. For this purpose sulphuric acid containing
about sixty-five to eighty-five per cent. H₂ SO, can be employed. This sulphate so
obtained, crystallises in the form of black-brown needles. This body is collected
and treated with water, when it decomposes, and the regenerated indigo separates
out in a physical condition that is fitted for use in all kinds of vats, it being
easily soluble, even in the fermentation vat, which acts particularly mildly.
The new readily soluble product is chemically indigo, but its physical condition
is changed by the treatment, and the change consists probably not merely in
fineness of division but in an essentially different molecular structure.
The following example will serve to further illustrate the nature of the inven-
tion and the manner in which it can be carried into practical effect; but the
invention is not confined to this example.
EXAMPLE.
Stir about one hundred parts of dry indigo, in the form of powder, into about
five hundred parts of sulphuric acid containing seventy five per cent. H₂ SO
Warm the mixture, whilst carefully stirring, to about thirty degrees Centigrade.
When the mixture is effected so that a uniform paste is obtained allow the mass
to stand for about an hour. The sulphate of indigo is then formed. To obtain
the indigo in the aforesaid new physical condition, add to the entire mass
about two thousand parts of water. Stir well, collect the new indigo by filtra-
tion and wash until free from acid. The new indigo retains its valuable property
of ready solubility in the vat even after drying.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed I declare that what I
claim is:-
1. The manufacture of indigo in a form readily soluble in all kinds of vats,
by treating indigo with dilute sulphuric acid, so as to obtain the hereinbefore

page_text: described indigo sulphate, and then treating this indigo sulphate with water
substantially as described.
2. The manufacture of indigo in a form readily soluble in all kinds of vats
in the manner described in the foregoing example.
3. As a new product the indigo readily soluble in all kinds of vats, such as can
be obtained substantially as herein before described and claimed.
Dated this 15th day of August 1900.
JOHNSONS & WILLCOX,
47, Lincoln's Inn Fields, London, W.C., Agents.