US2017295A - Photographic developer - Google Patents

Description

Patented a. 15, 1935- UNITED STATES PATENT) OFFICE 2,017,295 riio'roeaarmc DEVELOPER velopers became developers could period of time.

been made to overcome the aforesaid Hermann Schiiltes,

assignor to Deutsche Golddeanstalt vormals Boessler,

Mainz-Mombach, Germany,

and Silber-Schei- FrankIort-on-the- Main, Germany, a German company No Drawing. Application Angnst 10, 1934, Serial No. 739,279. In

Germany December 8, 1933 4 Claims. (Cl. 95-88) g dark; As a result such prior not be kept very well for along Although many attempts have tage, no attempt, as far as I am aware, has been wholly satisfactory and successful when carried into practice on a. commercial and practical scale.

I have discovered a photographic developer which overcomes the aforesaid disadvantages of prior developers and which possesses many advantages.

It is an object of the invention to provide a photographic developer which is not highly sensitive to oxygen and which produces a clear, un-

faded negative.

It is also within the contemplation of the invention to provide a photographic developer which is wholly satisfactory in practical use and which is commercial and is 'capableof being manufactured on an industrial scale.

Other objects and advantages of the invention will become apparent from the following description.

According to the present discovery, it has been found that pyrogallol monomethyl ether possesses the advantages of pyrogallol as a photographic developer while at the same time being free from the disadvantage of high sensitiveness to oxygen. With the present developer, perfectly clear unfaded negatives can be produced.

It has likewise been discovered that homelogues of wrogallol monomethyl ether can also be used as photographic developers. Thus; for instance, monoethyl ether of pyrogallol or monomethyl ether of methyl pyro allol canbe' employed instead of pyrogallol monomethyl ether.

For. the

PHIPQ E of Giving those skilled in the disadvanart a better understanding brine iri viition, the r following specific and illustrative example is giv- Solution A A photographic developer is prepared with 5 about 100 parts by weight of water, about 65 parts by weight of sodium sulflte and about 1.7 parts by weight of potassium pyrosulflte. To this solution about 1.7 parts by weight of pyrogallol monomethyl ether or pyrogallol monoethyl ether are added.

Solution B A solution is made by dissolving about parts by weight of soda crystals (sodium car- 5 bonate) to about 100 parts by weight of water.

About equal volumes of Solution A, of Solution 13 and of water are mixed together to give-a developer. The recipe and the handling of the developer is essentially the same as that of pyro- 20 gallol.

It is to be observed that the present invention is a surprising discovery which could not. have been predicted by those skilled in the art. This is particularly true because prior experiments have shown that pyrogallol 1.3 dimethyl ether is practically ineffective as a developer.

Furthermore, it is to be noted that pyrogallol monomethyl ether can be easily produced by partially. demethylating the dimethyl ether according to known method. It is likewise possible to convert pyrogallol into monoethyl ether 'by treating it with dimethyl sulfate. A very good yield:1 may be obtained in this latter process.

I aim:

l. A photographic developer containing a pyrogallol monoalkyl ether.

4. A photographic developer containing mon0- -methyl' ether of methyl pyrogallol.