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Author: Subject: Persulfate cell - Please translate passage (German)
jimmyboy
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[*] posted on 14-8-2008 at 11:31
Persulfate cell - Please translate passage (German)


If anyone could translate this - I would appreciate it -- having all the details would help

http://www.versuchschemie.de/upload/files/perox.gif

thanks
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12AX7
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[*] posted on 14-8-2008 at 18:55


Out of hand, the important stuff looks like: platinum electrodes, in an H2SO4 / KHSO4 solution, 8-12V(!!) applied, 0.48 A/cm^2, temperature not over 7°C, and I'm guessing precipitate was found after 10-15 minutes, which was recrystallized (something about 30°C), washed, tested for sulfate with BaCl2 and dried over conc. H2SO4 and CaCl2; 3 hours for 27g, 34% yield.

That sounds like most of it, but you probably guessed as much, so I shall yield the floor to someone who actually knows German...

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[*] posted on 14-8-2008 at 19:25


Quote:
Originally posted by jimmyboy
If anyone could translate this - I would appreciate it -- having all the details would help

http://www.versuchschemie.de/upload/files/perox.gif

thanks


There are online translation apps but I would need you to repost that page as a pdf rather than a gif so I can do an OCR scan on it.




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[*] posted on 14-8-2008 at 20:42


Try a U2U to one of our several Dutch forum members - are there any Geman?. They know German. I would not presume to suggest, but I don't think 12AX7 is far off the mark.

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[*] posted on 15-8-2008 at 02:21


Since that page is from Brauer, you'd think that the place to look for an English translation would be...the English translation of Brauer.

Other books have slightly different takes on the same thing.
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woelen
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[*] posted on 15-8-2008 at 03:39


Potassium peroxodisulfate is prepared by means of electrolytic oxidation (see reaction eq.) of a saturated solution of KHSO4.

The electrolysis is performed in a 500 ml beaker, which is placed in a larger container with a lower and an upper connection, such that it can be cooled intensively with icecold running water.

In the middle of the 500 ml beaker, a clean platinum sheet electrode is placed, with size 1.5 cm x 4 cm and this is used as anode. Parallel to the sheet, two other electrodes are placed, one at each side of the sheet, each having an area of 15 square cm, and made of platinum-gauze (no massive platinum sheet, it should be possible that liquid is running through). These two platinum-gauze electrodes are used as cathode. Before performing the electrolysis, the anode must be heated for a while, such that it becomes red hot and then it must be allowed to cool down again.

The beaker must be filled with a saturated solution of KHSO4 in dilute H2SO4. The cell must be connected to a powersupply (8 .. 12 V) through a series resistor and the resistor/voltage combination must be adjusted, such that the total current is 5.3 A (0.48 A per square cm on the anode). This current must be maintained for several hours, and in the meantime the beaker must be intensively cooled by means of a water flow through the larger container. The temperature of the KHSO4-solution may not go above 7 C during the electrolysis process. Appr. 15 minutes after starting the electrolysis the first visible amounts of K2S2O8 are formed, the liquid becomes somewhat turbid. DUring the electrolysis the very fine crystalline powder of K2S2O8 settles at the bottom.

When electrolysis is stopped, then the very fine crystalline precipitate is filtered on a glass-fritte by means of suction and then it is rinsed with a small amount of cold water. Small amounts of trapped sulphuric acid can be removed by repeated recrystallization from water at 30 C. The pure substance, which does not give any visible precipitate with BaCl2, can be pressed to make it as dry as possible and then it must be dried in an exsiccator over conc. H2SO4 or dry CaCl2.

Yield after 3 hours of electrolysis: 27 grams, which is 34% from theoretical yield (based on current of 5.3A for 3 hours).

[Edited on 15-8-08 by woelen]




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jimmyboy
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[*] posted on 15-8-2008 at 23:27


Thanks Woelen -- your right.. its Brauer - figures :)

[Edited on 16-8-2008 by jimmyboy]
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[*] posted on 25-8-2009 at 13:48


I did have a pathetic attempt with Graphite electrodes... erosion was rapid and no ppt I'm afraid.

Pt it is.

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[*] posted on 25-8-2009 at 14:03


Ive wanted to make my own persulfate for aes but yes platinum electrodes are essential but unfortunatly the electrodes described in the literature would cost >£100 :(
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kclo4
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[*] posted on 25-8-2009 at 15:35


Are you sure lead isn't an option? Works in other persulfate cells.



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Picric-A
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[*] posted on 26-8-2009 at 00:57


i believe lead gets oxidised to the dioxide which then dissolves ect, so no i think lead is out.
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[*] posted on 26-8-2009 at 01:06


According to this;
http://books.google.co.uk/books?id=E_u9ARrm37oC&pg=PA274...

Lead dioxide can be used... when i tried it with lead electrodes i found supposed lead dioxide produced dissolved. Am i doing something wrong here?
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kclo4
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[*] posted on 26-8-2009 at 16:04


How would it have dissolved?
Discribe what you saw a little bit better please.




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dann2
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[*] posted on 27-8-2009 at 15:58


Have a look at:

http://www.journalarchive.jst.go.jp/jnlpdf.php?cdjournal=bcs...

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[*] posted on 30-8-2009 at 13:01


The book Per-acids and their salts also has some useful info on persulfate electrolysis. It can be found at google books or archive.org.
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