US984442A - Process for preparing indoxyls and indigo coloring-matters. - Google Patents

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must be considered practlcable one whlc UNITED s'TATEsrntr NT OFFICE,

ARNOLD BAHTJEN, or

HAMBURG, (383E131);ANY:v

PROCESS FOR PREPARING INDOXYLS AND INDIGO COLORING-MATTERS.

To all whom it may concern:

Be it known that I, ARNOLD RAHTJEN, asubject of the German Emperor, and resi dent of Hamburg, Germany, have invented certain new and useful Improvements in Processes of Preparing Indoxyls and Indigo Coloring-Matters, of which the following is a specification.- I

7 It is a well known fact that substances which contain the group NHCH CO one or more times in the molecule may be converted by melting with alkali hydroxids into indoxyls from which indigo may be prepared inthe well known manner. However, the yields obtained by this process, as, for instance, whenv phenylglycinv (anilidoaceticaeid) is' used, are so small that the process s a commercially imcannot be employed for the manufacture of indigo on a large scale. It has been new found that an excellent yield of indoxyls and, consequently, of indigo maybe obtained by electrolyzing of a diaphragm;

substances of the aromatic or cyclic type and containing an aryl group linked to one on more groups of thegeneral type (NRCH CO), in which It represents hydrogen or an organic radical, in admixture with bodies capable of yielding metal ions upon electrolysis, such as the alkali hydrates, singly or admixed, oxids or hydrates of alkaline earths, or electrolyzable salts of alkalis or alkaline earths capable of yielding metal ions. Substances which serve as fluxes or diluting a ents maybe en'lployed, advantageously. El ectrolysis' may be carried out with or without the employment The experiments made to date have given yields up to and beyond 7 0% (seventy per cent.) of the theory.

In general it may be stated that substances of the aryl-glyciu type are suitable for employment in this process, including under this generic term the aryl-glycins pe-r -se and their homologues, esters and salts, as well as their acet-yl and othef'derivat-ives. When phenylglycin (C H NHCH COOH) is em Specification of Letters Patent. Patented Feb, 14. 1911, Application filed November 2, 1910. Serial No. 590,340.

ployed, the reaction which occurs is sometimes written as follows:

fsc

water being eliminated from the phenylglycin with formation of indoxyl. Equations such as this must be taken, however, as purely theoretical and as merely indicative of probable reactions, rather than as representing ascertained facts. This result could not have been anticipated, for it might have been expected that theorganic bodies employed,"such as salts of phenylglycin, etc., would be entirely decomposed by the electric current. Such is not the case, but with sensitive substances it is often useful to employ a diaphragm whereby the hydroxyl ions, "which are prejudicial, may be. conveyed in the simplest possible manner into phe anode chamber and thus rendered harmess. v

The favorable result of employing the electric current appears to reside in the fact that the alkaline meta-l is'enabled to react in stat-u mzsccndi and in a state of fine divi sion that cannot be obtained by mechanicalmeans.

The ten'iperature of the materials, and

the tension and the density ofthe current employed may vary between large limits.

Good outputs are obtained when the electrolysis'is carried on at a temperature between 160-300 degrees C. and with -1 to 10 volts and 0.2 to 20,;a mpe'res per square decimeter of surface of -.electrodes.

Typical substances which may be employed are, phenylglycin-phenylglycin and phenylhydantoin as well as their homologues, salts, ethers, etc., and their acetyl and other derivatives.) The electrodes and diaphragms emplo 'ed maybe those usually utilized for electro yzing alkali hydroxids,

-alkali hydroxids' alone.

free in molecular form, into the period of formation type and treating In a typical example of my invention, 100 parts of a molecular mixture of sodium and potassium hydroxids are mixed with 30 parts of acetylphenylglycin-o-carbonate of potassium and the mixture heated to about 220 to 260 degrees C. and fused in the cathode chamber of a suitable electrolytic cell. The anode Chamber may be charged with the-same molecular mixture of the The mixture in each chamber may contain alkaline earths or salts and alkalis or alkaline earths or diluting fluxes. The cell may serve as a cathode and carbon be employed as an anode. The electrolysis may be advantageously carried out wit-h a current of about 4 to 6 volts and about 2 to 5 amperes per square decimeter, the liquid mass being well stirred. The operation is continued until for each molecule of substance a little more than one atom of alkali metal has been set free, which may easily be calculated with the aid of the givendata. After cooling down the molten mass, it may be introduced into water and the indigocoloring matters prepared in the well known manner. mode of operating, as that have been made, of the theory.

Suitable precautions may be taken during the electrolysis to obviate or remove byproducts of the reaction, such as free alkali metal and water.

During the electrolysis, suitable reactive gases or vapors such as ammonia or hydrazin may be conveyed through or over the mass in order to convert liberated sodium etc., set

corresponding metal amids or metal imids. The re action may be carried out under reduced pressure or vacuum and I preferably carry out the electrolysis in a vigorous or lively manner at the beginning, and during the of water so that the water formed is at once rendered harmless.

Having now fully described my said invention, what I claim and desire to secure by Letters Patent, is-

'1. A process of preparing indoxyls and indigo coloring bodies which comprises electrolyzing a mass comprising alkali hydrox ids and a substance ot the aryl-glycin type, and treating the resulting mass to'recover indoxyl and indigo theretrom.

2. A. process of preparing 'indoxyls and indigo coloring bodies which comprises electrolyzing a mass comprising alkali hydroxids and other electrolyzable inorganic substances andra, substance of the aryl-glycin Hie resulting mass obtained to recover indoxyl and indigo therefrom.

3.A process of preparing indoxy'ls and The output with this shown by experiments is about 70 per cent.

indigo coloring bodies which comprises electrolyzing a mass comprising alkali hydroxids and diluting agents and a substance of the aryl-glycin type and treating the resulting mass obtained to recover indoxyl and indigo therefrom.

at. A. process of preparing indoxyls and indigo coloring bodies \vhichcomprises elec trolyzin a mass comprising alkali hydroxids mixed with fluxes and a substance of the aryl glycin type and treating the resulting mass to recover indoxyl and indigo therefrom.

A process of preparing indoxyls and indigo coloring bodies which comprises elec' Irolyzin a mass comprising alkali hydroxids and otherelectrolyzable inorganic substances and diluting agents and a substance of the aryl-glycin type and treating the resulting mass obtained to recover indoxyl and indigo therefrom.

6. A process of preparing indoxyls and indigo coloring bodies which comprises electrolyzing a mass comprising alkali hydroxids and other electrolyzable inorganic substances and fluxes and a substance of the aryl-glycin type and treating the resulting mass obtained to recover indoXyl and indigo tl'ierefron'i.

7. A process of indigo coloring trolyzing a mass comprising an alkali hydroxid and a substance of the -aryl-glycin type and during such electrolysis removing by-products of the reaction, and treating the resulting mass obtained to'recover indoxyl and indigo therefrom.

8. A process of indigo coloring bodies Which comprises elecpreparing indoxyls and trolyzing a'mass comprising an alkali hy-- droXid and other substances capable of evolving metal ions, a fiuxing body, a dilutbody and a substance of the aryl-glycin type, and treating the resulting mass obpreparing indoxyls and bodles which comprises elec- I Jjb taincd to recover indpxyl and indigo therefrom;

9. A process of preparing indoxyls and indigo coloring bodies which comprises electrolyzing a mass comprising alkali hydroxids and a substance of the aryl-glycin type and during such electrolysis contacting areactive gas with such mass to prevent formation of free metal, and treating the resulating mass obtained to recover indoxyl and indigo therefrom.

10. A process of preparing indoxyl' and indigo coloring bodies which comprises eleclrolyzing a mass comprising alkali hydroxids and a substance of the aryl-glycin type, the electrolysis being carried on with an increased current during the formation of water so that the water formed is at once rendered harmless, and treating the result- I ing mass obtained to. recover indoxyl and indigo therefrmn.

It. A process of preparing indoxyls and indigo coloring bodies, which comprises electrolyzing a mass comprising alkali hydroxids and a substance in which an aryl. group is. linked to the group NROH2(JO and treating the resulting mass to produce indigo coloring bodies.

12. A process of preparing indoxyls and indigo coloring; bodies, which comprises electrolyzing a mass comprising alkali hydroxids and a substance in which-a phenyl 'roup is linked to the group -NR-CH 10-, and treating the resulting mass to produce L5 indigo coloring bodies.

In testimony whereof I have hereunto set my hand in presence of two Witnesses.

' ARNOLD RAHTJEN. Witnesses:

ERNEST H. L. MUMMEN Horr, IDA. CHRIST. HAFERMAN'N.