Sciencemadness Discussion Board
Not logged in [Login - Register]
Go To Bottom

Printable Version  
Author: Subject: Orange stuff
Markovfff
Harmless
*




Posts: 12
Registered: 7-11-2017
Member Is Offline

Mood: No Mood

[*] posted on 3-12-2017 at 11:44
Orange stuff


Hi,
Chlorate cells use chromates/dichromates or other additives to prevent reduction of chlorate at the cathodes. They are Used together with ss, graphite cathodes, that is what I know.
I searched a lot of forums and tutorials to find anything about using dichromate with titanium cathode. Found nothing. I heard that titanium does not reduce chlorates but then i saw people adding it to the cell... Im confused.
So adding it to the electrolyte will do someting, or its just a waste of resources? Also whats the dichromate influence on mixed metal anodes? I encountered (maybe 2,3 times) people saying that it can even damage the anode, they talked about covering the anode with a layer of something... How? I don't know.

[Edited on 3-12-2017 by Markovfff]
View user's profile View All Posts By User
symboom
International Hazard
*****




Posts: 644
Registered: 11-11-2010
Member Is Offline

Mood: Feeling Ascaridole

[*] posted on 3-12-2017 at 14:26


Chromates /dichromates are to prevent chlorates from being reduced by the cathode it is to improve yield not necessary required another thing people do to improve yield is adjusting the pH in the optimal range.

[Edited on 3-12-2017 by symboom]




Chemistry video storage (1000 videos so far)
https://www.mediafire.com/folder/kbll6gz9bdb4q/Videos
Natures Intellectual Organic Peroxide. >>Ascaridole <<

Oxone
Used for the production of --> CH2O/Cl2/ClO2/Br2/I2

------------------------------------->>Hydrogen Peroxide << -------------------------------------------- >> Acetylene <<
Peroxide Salts
Zinc Peroxide <\> Copper Peroxide <\>Silver Peroxide <\>Lithium Peroxide <\>Magnesium Peroxide <\>Calcium Peroxide to Calcium Superoxide
CoO2. \\ NiO2 \\ Ti/V/Cr peroxy complex \\ Triamine chromium peroxide \\ LiH \\SiO2-H2SO4 (SSA) \\ [Ni(NH3)6]

Exotic reducing agents
Ga2O TiCl2 GeCl2 && Na2S2O4
View user's profile View All Posts By User
yobbo II
National Hazard
****




Posts: 279
Registered: 28-3-2016
Member Is Offline

Mood: No Mood

[*] posted on 3-12-2017 at 17:10


There are vast amuonts of nonsence out there on the web when it comes to chlorate making. All starter chemists/hobbyists have a go at chlorate. There are alot of cases of what monkey sees, monkey does. You neeb to add chromate becauce I read it somewhere etc.
Don't add any. What are the problems associated with removing it from the final product and possible problems if not removed properly?
Just use a small cathode that is well distributed around the anode.

See the bottom of this link
https://geocitieschloratesite.000webhostapp.com/chlorate/rea...

Yob
View user's profile View All Posts By User
Markovfff
Harmless
*




Posts: 12
Registered: 7-11-2017
Member Is Offline

Mood: No Mood

[*] posted on 6-12-2017 at 07:13


I still didn't get answers for my questions. My curiosity still isnt satisfied :V
View user's profile View All Posts By User
yobbo II
National Hazard
****




Posts: 279
Registered: 28-3-2016
Member Is Offline

Mood: No Mood

[*] posted on 6-12-2017 at 20:23


https://geocitieschloratesite.000webhostapp.com/chlorate/cat...

Some more info

The chromates form a layer on cathodes which effectively lowers there surface area without the disadvaantage of raising cell voltage.
Just use a small (sensible size) cathod to keep current density high on cathode. Dont have areas of cathode with low cd like for example the "back"sides. Use perforated cathodes.
Chromates are used by manufacturers to obtain small very important gains in current efficency. Not worth bothering about in amateur cells because of extra hassle of removal from product.
Smaller cats will raise v a small amount but it will hardly be noticable. The serious manufacturer could not tolerate this small rise.
View user's profile View All Posts By User
Markovfff
Harmless
*




Posts: 12
Registered: 7-11-2017
Member Is Offline

Mood: No Mood

[*] posted on 6-12-2017 at 23:21


Thank you, this is what I was searching for.

[Edited on 7-12-2017 by Markovfff]
View user's profile View All Posts By User
yobbo II
National Hazard
****




Posts: 279
Registered: 28-3-2016
Member Is Offline

Mood: No Mood

[*] posted on 8-12-2017 at 13:06


http://www.sciencemadness.org/talk/viewthread.php?tid=62495

This thread is useful.

Yob
View user's profile View All Posts By User
woelen
Super Administrator
*********




Posts: 6464
Registered: 20-8-2005
Location: Netherlands
Member Is Offline

Mood: interested

[*] posted on 11-12-2017 at 04:07


I do not agree with yobbo II. Some years ago I made a few batches of KClO3 from KCl, using a small MMO anode and a titanium cathode. Adding some dichromate makes a BIG difference. It is remarkable how little dichromate is needed for good results, but adding no dichromate at all makes production very inefficient. Separating dichromate (or chromate) from the potassium chlorate is not difficult at all, due to the excellent crystallization properties of KClO3.

See this webpage, I made a fairly extensive write-up of what I did:

http://woelen.homescience.net/science/chem/exps/miniature_ch...




The art of wondering makes life worth living...
Want to wonder? Look at http://www.oelen.net/science
View user's profile Visit user's homepage View All Posts By User
yobbo II
National Hazard
****




Posts: 279
Registered: 28-3-2016
Member Is Offline

Mood: No Mood

[*] posted on 11-12-2017 at 15:31



The cathode being used in the write-up is a classic example of the type of "layout" that is going to maximize hypochlorite reduction at the cathode in a cell without chromate. The cathode is somewhat large (not excessively) and is going to have low current density on the side of the cathode away from the anode (the dark side shall we say). This promotes hypochlorite reduction as I understand it.
It would be interesting to use a cathode that is quarter the area, drilled like the anode and placed both sides of the anode. Or perhaps use the same arrangement with a plastic cover on the cathode "dark side" or just use a piece of wire for the cathode and run without chromate.
My bottom line is that cathodic reduction can be controlled or eliminated by physical means (electrode geometry and position) as opposed to chemical means (chromates).
There must be some advantage in doing it the chemical way or the big manufacturers would not be doing it. In a proper industrial cell the anode and cathode are very close together (mm's) and using small cathodes would lead to current distribution problems on the electrodes? Not a problem when electrodes are an inch apart or so. There is also other advantages of using chromates like corrosion reduction in plant equipment, though this may be more historical nowadays.
Copied below from the net....

Helps prevent corrosion of Fe Cathodes.
Helps to buffer the electrolyte in the pH range 5 to 7 (pH control used).
Inhibits Oxygen evolution at the Anode.
Suppresses ClO- and ClO3- reduction reactions by forming a Cr3O4 film on the Cathode. It effectively raises the cd on the Cathode.
Supresses Perchlorate formation at high Chlorate concentrations in the Chlorate cell. (according to JAE 1 (1971) 207-212)





I have not measured current effeciency in a cell with small cathodes versus a chromate cell with the same or comparable cathodes so I could be wrong.

It would be a great experiment to set up the cell as Woelen has done, run some time untill bubble production stabalized, then add a plastic cover to the back of the cathode and see of bubble production increases and temperature of cell decreases (less hypochlorite reduction).
Chromate can be removed with barium chloride as barium chromate is insoluble if doing a sodium chlorate cell.

Get with the times. Go Green!

Yob

[Edited on 11-12-2017 by yobbo II]
View user's profile View All Posts By User
Markovfff
Harmless
*




Posts: 12
Registered: 7-11-2017
Member Is Offline

Mood: No Mood

[*] posted on 14-12-2017 at 11:28


What would be the optimal grams per liter dichromate level? I remember making electrolyte for my 2nd cell, and had read to use about 2-5g/L of solution, I think thats definietely to much. I even had trouble with dissolving it( potasium dichromate) and ended up on filtrating the solution to get the remaining dichromate out.
View user's profile View All Posts By User
woelen
Super Administrator
*********




Posts: 6464
Registered: 20-8-2005
Location: Netherlands
Member Is Offline

Mood: interested

[*] posted on 18-12-2017 at 03:48


In my cell I used a few tens of mg, for 100 ml of liquid. I would say, try with 300 mg. Your solution will have a bright yellow (not orange) color.



The art of wondering makes life worth living...
Want to wonder? Look at http://www.oelen.net/science
View user's profile Visit user's homepage View All Posts By User
Markovfff
Harmless
*




Posts: 12
Registered: 7-11-2017
Member Is Offline

Mood: No Mood

[*] posted on 19-12-2017 at 11:01


Thanks, currently runing a 6L cell, adding dichromate made a huge difference. Even if looking only on the temperature: went down from 63C ( and If I would let it go, it would get probably to 70-75C) to stable ~55C.

[Edited on 19-12-2017 by Markovfff]
View user's profile View All Posts By User
yobbo II
National Hazard
****




Posts: 279
Registered: 28-3-2016
Member Is Offline

Mood: No Mood

[*] posted on 4-4-2018 at 13:30


Document attached on additives and alternatives for Na dichromate for chlorate cells.

Attachment: afa_sd-0038-01-aa_en.pdf (1.9MB)
This file has been downloaded 42 times

View user's profile View All Posts By User

  Go To Top