Improvements in the Manufacture of Dyestuffs of the Phthaleine Series.
Year: 1898

page_text: Date of Application, 29th Aug., 1898-Accepted, 15th Oct., 1898
COMPLETE SPECIFICATION..
Improvements in the Manufacture of Dyestuffs of the
Phthaleine Series.
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I, OLIVER IMRAY, of Birkbeck Bank Chambers, Southampton Buildings, in the
County of London, Chartered Patent 'Agent, do hereby declare the nature of this
invention (which has been communicated to me from abroad by the Firm Basle
Chemical Works," of Basle, Switzerland) and in what manner the same is to be
performed to be particularly described and ascertained in and by the following
statement:
-
In the technical employment of the colouring matters formed by the alkyl ethers
of the dialkyl-rhodols, (products of condensation of the dialkyl amido-oxybenzoyl
benzoic acids with resorcinol) their commercial value is prejudiced by their sensi-
bility to alkalies and by the fact that the shades of the lakes they form with oxide
of zinc are converted, when steamed, from a yellowish red into a bluish violet.
My correspondents have now found that by combining the said ethers of dialkyl-
rhodols with formic aldehyde, well characterized products of condensation are
obtained, giving shades which are not altered by alkalies. The lakes formed by
these products with oxide of zinc yield shades which, on steaming, remain un-
changed.
These properties impart a high commercial value to the new colours, which
are yellowish red colouring matters.
The product which gives the most decided yellowish shade is obtained by the
action, of 1 molecule of an alkyl ether of a dialkyl rhodol on 2 molecules of formic
aldehyde. The following has been found to be the best way of working the
process:-
EXAMPLE.
To a solution of 42 kilogrammes of the ethylether of dimethyl-rhodol in 200
kilogrammes sulphuric acid of 66° Be. is added a mixture of 16 kilogrammes
formic aldehyde of 40%, and 100 kilogrammes sulphuric acid of 66° Be. The
reaction sets in at once and is marked by a rise of the temperature of the solution.
To complete the reaction it is allowed to stand for some days at ordinary tempera-
ture and afterwards it is poured on ice. The sulphate of the product of condensa-
tion remains in the solution and is separated by a solution of common salt as a
concreted resinous paste from which the remaining liquid can be decanted.
The sulphate is converted into the chloride by dissolving the former in 60 kilo-
grammes of alcohol and 70 kilogrammes water and by adding to the hot solution
70 kilogrammes of hydrochloric acid of 200 Be. After some time a solution of
common salt is poured in under stirring; the chloride is thus precipitated as a
thick paste, which can be separated from the liquid by decanting the latter.
In its dry form the product of reaction appears as a greenish brilliant powder.
It is soluble in hot water and in alcohol. Its alcoholic solution shews no
fluorescence, differing in this from the starting material. In concentrated
sulphuric acid the colour dissolves with a yellowish brown tint.

page_text: My correspondents have not succeeded in getting the new product in crystalline
form. From the solutions it separates as a resinous paste.
The new product of condensation dyes tannin-mordanted cotton a yellowish red
and on printing with oxide of zinc it yields a lake of the same yellowish red colour
which is not changed by steaming. The alkyl ethers of the dialkyl rhodols may
be condensed with 1, 2 or 3 molecules of formaldehyde yielding in all cases a
more or less yellowish red dyestuff.
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. A process for the production of dyestuffs of the phthaleine series, which con-
sists in condensing an alkylether of a dialkylrhodol with formic aldehyde sub-
stantially as described.
2. As new products the colouring matters obtained by means of the process
referred to in the preceding claim.