Sciencemadness Discussion Board - Bought Ferric chloride hexahydrate - colour?

Bought Ferric chloride hexahydrate - colour?

CHRIS25 - 22-2-2013 at 15:33

Took delivery of ferric chloride hexhydrate today, bit concerned about it. It is a soggy kharki army dirty green rather than a yellow. Does this sound suspect? Came from a reputable company, scichem uk. The inside of the lid has a few expected yellow stains, and the consistency is quite wet with yellow crystals dotted around the kharki army dark green soggy lumps.

Vargouille - 22-2-2013 at 16:17

According to Wiki:

Quote:

The colour of iron(III) chloride crystals depends on the viewing angle: by reflected light the crystals appear dark green, but by transmitted light they appear purple-red.

This could be part of it.

Ozone - 22-2-2013 at 16:36

It should be slightly moist (or so it appears) lumps. They are reddish/orange in color. It has a characteristic odor, and is a hydrolyzing metal salt so aqueous solutions (which are orange (dilute) to dark red/brown concentrated) are strongly acidic. Solutions are not stable above pH 4.0 (or so) above which the insoluble hydroxide precipitates.

It is deliquescent. And old samples may be soupy, frequently with the (light reddish-brown hydroxide stuck to the walls of the container.

Ferrous (II) chloride is green

Cheers,

O3

IrC - 22-2-2013 at 21:25

Yes it normally looks dark green when you are looking at a large pile of it fresh out of a well sealed bag where it has been kept completely sealed from any air containing moisture. I have pounds of it from years of making my own PCB etchant solutions. The solution gets unbelievably hot as you add it to water. Never bothered to do the math to compare but I think it evolves more heat than making a solution of lye. Chemistry I have played with for over some 50 odd years but never studied it to the level of the real experts here since electronics and physics has always been my greatest interest.

But trust me don't mix up a large batch of etchant in a plastic container, you can store it in plastic after it has cooled down enough. My first try at making my own etchant melted the container and the orange brown stains still exist to this day. What can I say you learn by doing. When I open a new bag it is just a fine powder, never really noticed a lot of lumps. I would think it has been exposed to moisture in the air if you find it to be very lumpy.

Just occurred to me reading your post again but you said it was soggy. You cannot store this chemical in a container with a screw on lid as moisture from the air over time will make a mess of it. Really should be in a plastic bag of the proper composition, metalized plastic, and hot sealed so no microscopic pathway to the atmosphere exists. Threads on a container lid are not a good enough seal. This I learned from experience. If you wish to keep it a fine dry powder it must be absolutely sealed.

[Edited on 2-23-2013 by IrC]

CHRIS25 - 23-2-2013 at 03:35

Hallo All who responded, thankyou. I am using it for reactions, notas an etchant, I have done a lot of etching but used copper chloride. I think I will return it because it came in a proper container, not with a screw on lid, it was from a reputable company where I get all my chemicals from. But it is Very Very soggy and the container weighs in at 535 grams. The product is a 500 gram delivery. The container weighs about 90 grams making the substance itself only 440 grams approx. this means that there must be less than 500 grams total. I think it has been exposed to too much moisture, the substance is definitely not red/brown, more yellowish/dark green.

[Edited on 23-2-2013 by CHRIS25]

IrC - 23-2-2013 at 06:54

Quote: Originally posted by CHRIS25

Hallo All who responded, thankyou. I am using it for reactions, notas an etchant, I have done a lot of etching but used copper chloride. I think I will return it because it came in a proper container, not with a screw on lid, it was from a reputable company where I get all my chemicals from. But it is Very Very soggy and the container weighs in at 535 grams. The product is a 500 gram delivery. The container weighs about 90 grams making the substance itself only 440 grams approx. this means that there must be less than 500 grams total. I think it has been exposed to too much moisture, the substance is definitely not red/brown, more yellowish/dark green.

[Edited on 23-2-2013 by CHRIS25]

I assumed screw on lid because you said "The inside of the lid has a few expected yellow stains". When you mix the dry powder with water to form etchant, anything the liquid touches leaves a very permanent stain which is somewhere in color of a mix of red/orange/yellow/brown depending upon the concentration of the solution that was spilled. While not applicable to your case color is also modified in hue if it has been used to etch copper previously. In effect the color you describe in the lid sounds like a normal etchant solution which has dried out. Meaning of course they sent it in a very poor container for ferric chloride storage. Point I was getting at was to answer your initial question 'is it ferric chloride'. Answer yes. Going further has it been exposed to moisture in the air, again yes. I cannot state too strongly how well sealed ferric chloride has to be if you want it in a pristine dry powder. It will grab water from the air right through a poor quality plastic bag, even one that has been sealed with a hot wire. If you are looking for it you should search for suppliers of etchant. Better sealed and very cheap.

One pound bags made of a thick metalized plastic are the common way I find them. These I store in a larger container with a screw on lid after I toss in a few packs of silica gel desiccant. I then seal the lid to the container with 3 inch wide black electrical tape to minimize anything getting through the threads. That is just to keep as much moisture as I can away from the outer surface of the bags. In 1987 I bought 20 one pound bags from Tri Tek in phoenix. Your question got me wondering since I have a few left so I opened one last night, had been stored as I described above the day I bought them 26 years ago. Dry as can be, fine powder. I went ahead and made up a few more gallons of etchant with it because once you cut open the bag storage is a no win scenario. I know this from past experience. I do not think buying Ferric Chloride is a good idea if it comes in a container sealed only with a removable lid. I would imagine you could store it in a nice glass jar with a ground glass stopper which had been coated with vacuum grease. Simply because to keep it dry the container should be in a perfect vacuum or inert gas I suppose, but one with a vacuum tight seal anyway.

CHRIS25 - 24-2-2013 at 01:25

Thanks for the long explanation, the hexahydrate should be yellow, or orange yellow which this is not. there are lots of images not least on another chemical company (http://mistralni.co.uk/products/ferric-chloride-hexahydrate) where I order where it is yellow. So I will be taking this back. It should not be a dirty green and have the consistency of mud, which it does. Nevermind, I think some worker must have scraped it off the ground.

[Edited on 24-2-2013 by CHRIS25]

IrC - 24-2-2013 at 12:23

Used the stuff many years but never delved all that much into the chemistry of it. Looking at mine carefully it is anhydrous. The image on the page you linked is what it looks like after a solution evaporates. So the color relates to both the water of crystallization and the angle of incident light as near as I can tell looking at what I have. Must be the difference between the 6 H2O's or lack thereof. Which gets confusing when you say yours is green but mushy which sounds to me like it has been exposed to moist air. Sounds like you are right floor sweepings is what they sent you.

Decided to look into it to be sure. Looked at the Wiki page:

http://en.wikipedia.org/wiki/Iron%28III%29_chloride

They show an image of a yellow pile of powder. Yet they state:

"The colour of iron(III) chloride crystals depends on the viewing angle: by reflected light the crystals appear dark green, but by transmitted light they appear purple-red. Anhydrous iron(III) chloride is deliquescent, forming hydrated hydrogen chloride mists in moist air".

The pic is not what I have. The verbal description is precisely what I have. And exactly how it acts which is why I have to work carefully with it, the acid vapor is unbearable. What we need is an expert like Woelen to clarify things.

What I have is I assume FeCl3, whereas you are trying to obtain FeCl3⋅6H2O.

Found a pic which is the appearance of the FeCl3 I have several pounds of.

[Edited on 2-24-2013 by IrC]

woelen - 25-2-2013 at 09:11

I have abhydrous FeCl3 and this is black with a metallic lustre, a little bit looking like iodine. I also have FeCl3.6H2O and this is mustard/yellow.

CHRIS25 - 25-2-2013 at 12:20

Yes irc that's right. Though I have never seen dark green hexahydrate on the web. Anyway Woelen's anhydrous I have seen. I took mine back today and got a refund. They don't make it and the company where they get it from does not make it, a bit like the horse meat scandal. I think it was dried out spent etchant, honestly.

elementcollector1 - 25-2-2013 at 12:22

In that case, it'd be FeCl2...