A ord in
Year: 1898

page_text: I, JACOB GROSSMANN, of Harpurhey Chemical Works, Manchester, in the County
of Lancaster, Manufacturing Chemist, do hereby declare the nature of this inven-
tion to be as follows:-
The use of hydrosulphites in indigo dyeing has hitherto been restricted to
easily soluble compounds of hydrosulphurous acid, chiefly hydrosulphite of soda.
I have found that there exist a number of almost insoluble or difficultly soluble
compounds of hydrosulphurous acid which in the present state of our knowledge
may be considered as normal or basic salts; such as the normal or basic calcium
hydrosulphite; the normal or basic zinc hydrosulphite and similar compounds,
which have the property of reducing indigo and which on account of being
difficultly soluble and comparatively stable are particularly useful for indigo
dyeing. For this purpose finely ground indigo paste and normal or basic calcium
hydrosulphite or a similar hydrosulphite or a mixture of the latter with calcium
hydrosulphite are mixed together at a suitable temperature and strength; lime may
be added if necessary, or a suitable quantity of a hydrate, carbonate, tricarbonate,
sulphate sulphite of alkali or ammonia or any other suitable soluble salts, either by
themselves, or mixed with lime may be added. Indigo white or a mixture of indigo
white and indigo may be used instead of indigo. The reduced indigo which
results from this process may be used as such or in conjunction with other suit-
able colouring matters reduced to leuco-compounds or with other vats and with
other reducing agents. The hydrosulphite of lime may be used in a pure or
impure state and may be prepared by precipitating a neutralized or alkaline
hydrosulphite of soda with calcium chloride or by any other suitable process.
Other hydrosulphites as such or as double compounds though not of the nature
of basic or normal salts may be used if they are sufficiently difficultly. soluble.
Dated this Third day of October 1898.
JACOB GROSSMANN.
A New or improved indige av.
I, JACOB GROSSMANN, of Harpurhey Chemical Works, Manchester, in the County
of Lancaster, Manufacturing Chemist, do hereby declare the nature of this inven-
tion and in what manner the same is to be performed, to be particularly described
and ascertained in and by the following statement:-
The use of hydrosulphite in indigo dyeing has hitherto been restricted to
easily soluble compounds of hydrosulphurous acid chiefly hydrosulphite of soda.
I have found that there exist a number of almost insoluble or difficultly soluble
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page_text: compounds of hydrosulphurous acid which in the present state of our knowledge
may be considered as normal or basic salts such as normal or basic calcium
hydrosulphite, a normal or basic zinc hydrosulphite and similar compounds
of the alkaline earths and of certain metals which have the property of reducing
indigo and which on account of being difficultly soluble and comparatively stable
are particularly useful for indigo dyeing. For this purpose finely ground indigo
paste and normal or basic calcium hydrosulphite or other suitable difficultly
soluble hydrosulphites or a mixture of the latter with calcium hydrosulphite are
mixed together at a suitable temperature and strength. Lime may be added if
necessary or a suitable quantity of a hydrate, carbonate, bi-carbonate, sulphate
sulphite of alkali or ammonia or any other suitable salts either by themselves or
mixed with lime may be added.
In order to prepare a stock vat of reduced indigo for feeding a dyeing vat I
proceed as follows:-The finely ground indigo paste is mixed with the necessary
quantity of milk of lime in a manner known to every practical dyer and heated
to about 40° to 50° C. with the addition of a suitable quantity of water; the
mass is agitated and calcium hydrosulphite preferably in a paste is added in
small quantities at a time slowly until the indigo has been sufficiently reduced,
which can be seen by the colour changing to the characteristic yellow or yellow
green of reduced indigo. When the best proportions have thus been ascertained
by slow and careful working subsequent operations may be carried on more
quickly on the basis thus established. The reduced mixture may be used for
feeding the dyeing vat which is kept in good condition by a further addition of
lime and calcium hydrosulphite when necessary. If it be preferred to prepare
a stock soda or potash or ammonia vat the free lime may be replaced by equiva-
lent or other suitable quantities of soda, potash or ammonia carbonate or other
suitable sodium potash or ammonia salts which by double decomposition with the
insoluble or difficultly soluble hydrosulphite form a soluble hydrosulphite; and
these alkali or ammonia compounds may be added to the dyeing vat also along
with calcium hydrosulphite or any other suitable insoluble or difficultly soluble
hydrosulphite. The insoluble hydrosulphites may also be used for reducing other
colouring matters, or colours capable of forming leuco-compounds which are used
in conjunction with indigo and in this case also the insoluble hydrosulphites
may be used by themselves or in conjunction with the carbonates sulphites sul-
phates or other suitable salts of the alkalis or of ammonia, and the end of the
reaction may be ascertained by the change in colour as in the case of indigo or
by other suitable tests known to chemists.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I declare that what
I claim is:-
1). The use of calcium hydrosulphite or other suitable difficultly soluble or
insoluble hydrosulphites for the reduction of natural refined or artificial indigo,
of derivatives or substitutes of indigo or other colouring matters forming leuco-
compounds, each of these colouring matters by themselves or mixed, but particu-
larly in conjunction with indigo, and the subsequent employment of these reduced
substances in dyeing as described above.
2). The use of calcium hydrosulphite or other suitable difficultly soluble or
insoluble hydrosulphites for the reduction and subsequent use in dyeing of
indigo by itself or mixed with other colouring matters as above in conjunction
with suitable salts of the alkali, or of ammonia, such as carbonates, sulphites,
sulphates, or other suitable compounds.
Toted th
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