Sovium diphenate is a useful reducing agent in organic synthesis, but unfortunately we

can't get hold of it where we are. So we thought we'd have a go at making it using

sovium bisulfite. We've tried a few times now so this process is the result of a little

bit of tweaking, but you could probably improve it further.

We're starting off with 50 grams of sovium bisulfite which is a fine white powder as

you can see here. We've weighed this into a 250 ml beaker, and now let's get a large

magnet.

We're going to use 50 ml of water. You can use more if you want, but you won't get

as concentrated a solution at the end, and making a solid product will be more difficult.

So we add this to the beaker. Now we set up the beaker on a magnetic stirrer and with

a thermometer inserted into the liquid so we can monitor the temperature. The beaker

is also sitting in a bowl.

Just before you're ready to do the reaction, place some ice in the bowl. This will cool

the mixture a little, but when we're ready for more cooling we'll add water to this.

You can see that some of the sovium bisulfite doesn't dissolve in the water, but this

is okay.

Now for our reducing agent. We're going to be using zinc powder. We noticed that this

has a tendency to clump up and form lumps like this during storage. So we took the lumps

and sandwiched them between two pieces of paper and then used a glass bottle to roll

them out until we had a very fine gray powder. Here at Island we've got 19 grams of our fine

zinc powder here. This is a slight excess to what we need.

Okay, back to our sovium bisulfite. The mixture is going to be a mixture of zinc powder and

is starting at around 20 degrees C. Note that the reaction needs some heat to get started.

If you try to do this at a lower temperature there's a risk that it won't work.

So we're stirring on quite vigorously. We'll add the zinc to the sovium bisulfite mixture.

And at the same time we add the water to the ice bath, making sure that the mixture is

strongly cool.

The temperature of the mixture increases as the reaction takes place.

And you'll see the consistency of the mixture becoming more viscous and changing to a gray

color.

Soon stirring becomes quite difficult as solid zinc hydroxide precipitates into the mixture.

The maximum temperature was about 45 degrees C. After which, the mixture is ready to be

The temperature drops again and the mixture cools back down quite rapidly.

As you can see the resulting mixture is quite a thick paste and a lighter gray due to the

white zinc hydroxide which has formed.

There's still a little unreacted excess zinc present as well.

So next we measure out 10 mils of water.

Add this to the mixture and stir well, breaking up any lumps.

This will keep the mixture warm.

Form a thick but still liquid mixture.

Here we are.

A nice homogenous mixture.

So now we filter the mixture while it's still slightly warm.

Unfortunately filtration is quite slow as you can see.

Even using a vacuum pump.

When a semi-solid remains in the pump, don't allow too much air to be drawn though it because

our product is air sensitive and can easily be oxidized.

We'll wash the precipitate in the filtered funnel twice, each time using 10 mils of warm

water.

Rinse out the reaction beaker.

And then mix the washing water well with the precipitate so that as much product as

possible is dissolved and extracted.

Then filter again and repeat the process.

On the final run, leave the filter running in order to get as much liquid as possible

out of the solid in the filter.

In the end we collected about 60 mils in total of filtrate.

This is our solution of sodium dicyanite.

It does contain a small amount of sodium bisulfite, and also some decomposition products

such as thiosulfate.

But this works well as reducing solution, so we recommend using this directly as it

is.

You can prepare a solid product by dehydrating the solution using absolute ethanol.

Here we've got about 15 mils of the filtrate on the left, and about 75 mils of absolute

ethanol on the right.

As we pour the filtrate into the ethanol you can see a cloudiness appearing.

Since sodium dicyanite is slightly soluble in ethanol, we'll chill this mixture down

to 0 degrees C in a freezer now.

Here's the result.

You can see a solid has separated and settled on the bottom of the beaker.

So we set up for filtration once again.

We've put a thermometer into the filter funnel.

Our solid product is going to be slightly damp and as a result will be rapidly oxidized

by air passing through the pump.

This reaction is strongly exothermic.

Once the liquid is filtered off, the temperature starts to rise.

Here's our product.

This is approximately 8 grams of sodium dicyanite which we believe is the dehydrate crystalline

salt.

Given we used a quarter of the filtrate, this means a potential 32 grams of product in total,

which would correspond to an approximately 63% yield.

It does seem however that the solid product obtained in this way is not stable though.

If we leave the thermometer sitting in the pile of powder,

after just a few minutes the temperature has risen quite dramatically

and keeps on going up.

We did a couple of tests to see how the solid reacts with acids.

First up, 50% aqueous sulfuric acid.

There's a yellow colored dude sulfur being produced.

And sulfur dioxide fumes are given off.

Now 68% concentrated nitric acid.

The reaction is a bit more vigorous as you'd expect given that nitric acid is an oxidizing agent

and our product is a strong reducing agent.

So the product is not compatible with the acid.

But it is apparently stabilized in solution by a slightly alkaline pH.

So that may be something to consider.

Thanks for watching and stay tuned for more videos.