DE2511433A1 - METHOD OF CLEANING PHOTO TANKS - Google Patents

Description

GERMAN GOLD AND SILVER SCHEIDEANSTALT

formerly Roessler? 51H33

6 Frankfurt / Main, tfeissfrauenstrasse 9 * "

Procedure for cleaning photo tanks

It is known to use lime and silver coatings in photo technology Devices such as developer trays and developer tanks with aqueous Solutions of potassium cyanide, nitric acid, with concentrated Sulfuric acid or with alkaline hypobromite solutions. Such means are not harmless and also from: .n From an environmental point of view, it is undesirable.

It is also known to use salts with a high oxidation potential such as potassium dichromate, potassium permanganate and cerium sulfate in acidic Solution to use for cleaning, see DT-AS 1 o6S 8 ^ o. The £, loop speed However, the silver is not large enough when more dilute solutions are used, so that more concentrated ones are also used here Solutions have to be used and thereby again environmental problems appear.

Alkali ferricyanides have also been used with thiosulfates as attenuators used, see DP (DDR) 23 3 ^ 8. For effective silver removal However, very concentrated solutions must also be used here.

It is also known to use thiourea to dissolve silver stains to be used, see the published German application B 19 4 ^ o IVa / 57b.

In contrast, it has now been found that there are silver stains in Have phototechnical devices removed quickly and safely, if aqueous solutions of alkali iperoxomonosulphate, alkali bisulphate and Thiourea with a content of 1o - 15o g / l alkali peroxomonosulphate, 2o - 2oo g / l alkali bisulfate and 5 - 100 g / l thiourea can be used to remove silver.

509849/0854

The specified amounts of the individual substances can vary with one another can be combined as required.

To prepare the solutions, peroxomonosulphate and bisulphate are used as a component of the mixture (α) on the one hand and on the other hand Thiourea - if necessary with 5 - 3o g sodium sulfate - as 2. Mixture component (b) dissolved. Thiourea and the oxidizing agent should not be "stored together.

Preferred amounts are 10-4o g / l alkali peroxomonosulphate, 100-18o g / l alkali bisulphate and 25-60 g / l thiourea. Alkali peroxomonosulfate is primarily understood to mean the potassium salt, while alkali bisulfate is primarily the sodium salt.

The solution temperatures are room temperatures or even higher Temperatures up to about 45 C are possible. Even the silver stains themselves can be treated with the solution in this temperature range.

The quantities of the mixing components A and B used are only so large that they are in no way harmful to the environment. Besides that the amounts of oxidizing agent are not sufficient to convert the sulfur in thiourea to a higher oxidation state in a shorter time] Time to convict.

The process of the invention is illustrated by the following examples explained;

example 1

With a cleaning mixture containing 45 g of potassium peroxomonosulfate, 40 g thiourea, 14o g sodium bisulphate and 25 g sodium sulphate '

p. Liters of solution, a thick silver deposit was dissolved in a photo dish within 2 minutes at room temperature.

Sulfur deposition did not occur.

Example 2 <*

The same silver coating was at the same temperature from a solution that p. Liter 22.5 g potassium peroxomonosulfate, 20 g Thiourea, 70 g sodium bisulfate and 12.5 g sodium sulfate contained, dissolved in about 4 min. The solution remained clear.

509849/0854

J 251U33

Example 3

With a solution of 11g potassium peroxomonosulfate, 1o g of thiourea, 35 S sodium bisulfate and 6 g of sodium sulfate in 1 liter of "water of the silver coating had disappeared after about 15 min..

Example h

The same silver coating was coated with a solution containing 115 g of alkali peroxomonosulfate, 30 g of thiourea and 70 g of sodium bisulfate per liter contained, dissolved in 3 min. A sulfur deposition took place after about 4 hours.

509849/0854

Claims (3)

Γ "- τ7" j NACHeER ^ IQHTi claims 1. A method for cleaning photo tanks, characterized in that that aqueous solutions with 1o - 15o g / l alkali peroxomonosulfate, 2o - 2oo g / l alkali bisulfate and 5 - 100 g / l thiourea can be used. 2. Photo tank cleaner made from mixture A with 1o - 15o g alkali peroxoraonosulfate and 2o - 2oo g of alkali metal bisulfate and mixture B with 5 - 100 g of thiourea. 3. Photo tank cleaner according to claim 2 with a content of sodium sulfate vo.n 5 - 3o g in mixture B. Ffm., 15-3.197 ^
PL / Dr Schae-F 509849 / 085A