Sciencemadness Discussion Board

Ferrocyanide synthesis --> thiocyanate

Random - 28-8-2012 at 09:52

Found this recipe, will it work? Is it safe? I don't want to handle any cyanide.
Quote:

Ferrocyanide Preparation Ferrocyanide is obtained by heating 10 parts (by weight) potassium (or sodium) carbonate; 10parts coke. cinders, or coal; and 3 parts iron turnings, all in coarse powder. to a full red heat inan open crucible, stirring occasionally until small jets of purple flame arc no longer seen. Whencool, the soluble matter is dissolved out of it, the solution filtered, evaporated, and crystallized.The crystals obtained are redissolved in hot water and cooled very slowly, forming large yellowcrystals of the ferrocyanide.In order to obtain a pure form, melt dried ferrocyanide in a glass vessel and let cool, dissolvethe fused mass in water, neutralize any excess of alkali with acetic acid (vinegar), andprecipitate the salt by adding strong alcohol to the solution. Wash the precipitate with a littleweak alcohol, redissolve it in water, and crystallize.


Then I will convert it to thiocyanate, by method I found on this forum:
Quote:

I just mixed up a batch of the stuff using a slightly different procedure also from Fownes. Since I did not have the potassium salt, I started with sodium ferrocyanide. I dehyadrated the sodium ferrocyanide by heating it, then added the sulphur, ground the two together to make a fine, well-mixed powder, heated again to melt the sulphur and kept the mixture at that temperature for a few minutes to react. When it cooled down, I added water to the resulting blackish mass and boiled to dissolve the thiocyanates. I then added Na2CO3 to precipitate the iron and filtered. Upon adding some FeCl3 to the filtrate, I got the deep red complex. This stuff is a dead ringer for blood! Later on, I may evaporate the filtrate and extract with alcohol to purify the NaSCN and see how the crystals look. In addition to its uses for the gag, this stuff is also useful as a test for iron. Also, it can be used as a starting point for making thiourea by a variation of Wohler's celebrated reaction --- prepare NH4SCN, then heat it to 180C to turn it into NH2SCNH2.


I need to know if these methods are safe, i don't wanna be producing any cyanide at all.

blogfast25 - 28-8-2012 at 11:47

Your ferrocyanide recipe lacks a credible source of nitrogen (air nitrogen being very unreactive). In Ye Good 'Ole days, animal protein (skin, hair, hooves, horns etc) would be added to that mix as a nitrogen source. Real smelly business. There's another thread on old style iron hexacyanides somewhere on this board.

[Edited on 28-8-2012 by blogfast25]

Random - 28-8-2012 at 15:38

Oh yeah i forgot about it

Ill probably use some casein or meat

Maybe i could use some urea,, gonna be stinky

Random - 28-8-2012 at 15:57

Oh yeah i forgot about it

Ill probably use some casein or meat

Maybe i could use some urea,, gonna be stinky

Magpie - 28-8-2012 at 19:50

You could also consider bloodmeal, available at your local garden supply store. I think it is just dried blood.

If you can get this synthesis to work it will be a useful achievement as the ammonium thiocyanate that I bought was rather expensive, IIRC.

Random - 29-8-2012 at 09:06

I will do it in microscale first

Do prussian blue and "iron blood" test, ill report results

unionised - 29-8-2012 at 10:35

I always wondered about this.
You make ferrocyanide by heating stuff then you destroy ferrocyanide by heating it.
How does it know which you are trying to do?

And I'd use dried milk rather than dried blood- slightly less stinky and (for most of us) easier to get.

Having said that, doubt the reaction is that specific. It may be a use for the horrible woollen jumper someone knitted for you.

blogfast25 - 29-8-2012 at 11:59

Quote: Originally posted by Random  
ill report results


Please do. Hexacyanoferrates and thiocyanates are expensive and very useful chemicals. A decent write up on something that works would be of interest to quite a few here.

Thumbs up!

Random - 29-8-2012 at 16:23

On a mobile, cant write much

Did a reaction with bicarbonate, steel wool, carbon and urea as nitrogen source

Heated it only for 8 minutes over a candle in a very small aluminium crucible

Aluminium melted and/or reacted with nahco3, took resulting mass and filteres a solurion


It was slightly yellow, no blue color was visible on addition of iron acetate.


Either urea doesnt work as nitrogen source or i didnt heat it enough

prussian blue test is very sensitive, nothing was formed


Ill try casein and heat it longer in small tuna can next time
blood is also iron source, but i have no access to it

Random - 29-8-2012 at 16:32

Just checked ferrocyanide is yellow

Maybe i made it but prussian blue is ferric salt

Maybe i should have oxidized it for prussian blue, oh well

blogfast25 - 30-8-2012 at 03:59

You need red heat I believe. A candle won't do.

AJKOER - 30-8-2012 at 11:16

A possible direct and proven approach to HCN (and then NaCN and NaSCN, but gaseous requiring precautions and use of an expensive catalyst), try to replicate the industrial Andrussow process either on a micro scale or larger. Per Wiki, to quote:

"The Andrussow process is an industrial process for the production of hydrogen cyanide from methane and ammonia in the presence of oxygen and a platinum catalyst.[1][2]

CH4 + NH3 + 1.5 O2 → HCN + 3 H2O

Side Reactions

This reaction is very exothermic. The change of Enthalpy of this reaction is equal to -481.06 kJ[3]. The heat provided by the main reaction serves as a catalyst for other side reactions.

CH4 + H2O → CO + 3 H2
2 CH4 + 3 O2 → 2 CO + 4 H2O
4 NH3 + 3 O2 → 2 N2 + 6 H2O

This side reactions can be reduced by only short exposures to the catalyst."

Link: http://en.wikipedia.org/wiki/Andrussow_process

The created HCN could be immediately be reacted with NaOH. Obviously, this reaction should only be attempted with appropriate safety equipment and ventilation being a gases reaction process.

Also, I suspect one may be able to successfully substitute C2H6 for CH4 with increasing air/O2 flow.

So, if one made a home-made Pt catalyst (Platinum jewelry turned into powder, or better, dissolved and freshly precipitated), even though less than the perfect catalyst, the reaction is reported as exothermic and best with "only short exposure to the catalyst", so a home-made low efficiency Pt catalyst may work. One may be able also to use a Ag/Al2O3 based catalyst (see full thesis at http://research.cems.umn.edu/schmidt/schmidtpapers/thesis/Sa... ). I would make such a Silver catalyst by the thermal decomposition of Silver oxalate (Aluminium oxalate).

However, further research does indicate that the process is intricate requiring a heat exchanger (see "Alternative catalyst supports for hydrogen cyanide synthesis and ammonia oxidation" by DA Hichkman, M Huff and LD Schmidt, published in Ind. Eng. Chem. Res., 1993, 32 (5), pp 809–817. Link: http://pubs.acs.org/doi/abs/10.1021/ie00017a007 ) to avoid a thermal decomposition of the highly unstable HCN:

HCN + H2O --> NH3 + CO

so nothing is ever really easy.