kallitype problems

[R Paul]

Hi guys
I made a couple of kallitypes the other day and I noticed that when I mixed the ferric oxalate and the silver nitrate,it had a yellow precipitate instead of a clear solution. Is that supposed to happen? I couldn't find anything in my books about whether the solution should be clear or not and what to do about it.
Also the solution dissolved the foam brush I was using. That I did not expect. But I did get an image at the end of it so I couldn't be too far off
Rob

 

[Andrew O'Neill]

When the two are mixed, they are clear but with a slight yellow hue. When you mix the two together, it turns yellow? Where did you get the ferric oxalate from? Your foam brush dissolving in the sensitizer is very odd.

 

[R Paul]

I made the ferric oxalate using the directions in Richard Faber's book. It ended up a nice clear green solution. I thought the brush melting was odd, I never heard of it happening before. What I get is a yellow liquid and a white precipitate when I mix the silver and the oxalate. Could there be too much oxalc acid left in the ferric oxalate?

Rob

 

[roncromberge]

Hello,
The white precipitate is silver oxalate. that is formed as is in the ferricoxalate residues of oxalic acid.
the ferricoxalate is not clean enough. the color of good ferricoxalate should be golden or amber. the more the color from yellow to green is meant more oxalic acid.

Greets,

Ron Cromberge

 

[Jim Noel]

I strongly suspect your Ferric Oxalate, particularly the ammonium hydroxide is the cause of all your problems.
Ferric oxalate is too cheap to worry about mixing your own. I mix about 90% of my chemistry from reagents, but not this one. I believe you will find it cheaper as well as more dependable to buy the powder.

 

[R Paul]

I thought the color worked in the opposite way, greener being better. Why would the ammonium hydroxide be a problem? If it was reacted with the ferric ammonium sulfate,any excess would be washed out when you washed the ferric hydroxide. Unless you mean that the variability of the amonnia concentration would throw the whole thing out of balance. I think that happened when I transferred the ferric hydroxide from the filter paper to a beaker. I could have lost enough to make a difference.
Jim you're probably right about buying this one,and now I can say I tried,and go buy it with a clear conscience
Thanks for the help,now I can fix it
Rob

 

[Andrew O'Neill]

I am not familiar with Richard Faber's book, or how he mixes up ferric oxalate, but it should be straight forward. When good quality ferric oxalate is mixed into hot distilled water, the resulting solution should be clear with a light brown/yellow tint, not green. I get ferric oxalate from Bostick & Sullivan. It is of very high quality and goes quite easily into solution at a high temperature.

 

[R Paul]

It really is a very good book,I have never had any problems with any of his methods until now. He actually synthesizes ferric oxalate from ammonia and ferric ammonium sulfate, the method seemed easy,until I tried it. He also recommended buying the ferric oxalate,but I couldn't resist the challenge. Well as I said before ,I tried and failed ,so now I can go buy the stuff with a clear conscience.
Thanks again for the help
Rob