25 replies to this topic

[mshaner]

Hello All,

I've just received my shipment of Pot. Dichromate that I was going to use to coat my Mg according to Shimizu's method. HOWEVER, as I read the MSDS sheet I'm noticing just how nasty this stuff is. I knew it was mean, but I'm a bit concerned as I don't have a $300+ self-contained breathing apparatus in my drawer.

Two questions:

1. Once this stuff is in the water and heating up, are the vapors harmful too? I would assume so..

2. If I use 2-5% of it in a composition as a combustion catalyst when does it become less harmful or does it?

Thanks,

Shane Heilman


PS I knew I needed a NIOSH approved apparatus and I have one, but not self contained....not completely ignorant of the facts, just want to be enlightened.

[dfk]

K2Cr2O7 Is supposed to be one of the most poisonous chemicals used in the hobby. I almost did the same thing as you only I read the sheet and changed my mind before I made the mistake of getting the stuff on my property and in my responsibility.
Its absorbable through skin as well as inhalation and is said to be carcinogenic.
I've also read its safe to work with when all precautions are taken, so the decision is yours. Another thing to note is, the water you end up with after your Mg treatment is toxic and should be disposed of accordingly; Improperly disposed waste may find its way into streams or worse drinking water, not too tasty.

What are you protecting the Mg from?
If it's not Ammonium perchlorate you can just use linseed oil.

[Creepin_pyro]

Don't know if this helps, but when my college labs deal with Potassium Dichromate solution, it is ALWAYS under a fume hood. Not sure about the dangers of working upwind with half decent breathing apperatus, though - I have just stuck to Linseed oil.

[BigG]

Pot. Dichromate vapours do not usually represent a hazard, although it is better to play safe and pour the solution onto the metal from a few meters away. Also, the effects of the chemical are more addressed toward people who use this on regular bases. Touching your skin once will not have future replications.

However ? this is a dangerous chemical. Generally, most amateurs that I work with tend to use linseed oil ? although Pot. Dichromate provides a better protection. The main problem is that after coated ? the magnesium particles represent hazard and they should not come to contact with skin + you should where a dust musk when handling the coated material.

[mshaner]

For your linseed coating do you use 75/25 acetone to linseed? This is what I've heard.

Shane

[BigG]

100% linseed. Why on earth would you need acetone?

[mshaner]

This was the suggested ratio by Gary Purrington of Firefox. I've also seen it on this site I believe...

Shane

[Yugen-biki]

When the Mg is treated using K2Cr2O7, can I put the Mg on the shelf and use it some days or weeks later? Or do I have to use it right away?

I don?t see why I can?t make a larger treating of Mg and use the same over a period of time. The K2Cr2O7 makes a oxide coating on the Mg, and why would this go away...? Am I right or wrong?

[BigG]

This was the suggested ratio by Gary Purrington of Firefox.  I've also seen it on  this site I believe...

Shane

It might serve to quick the drying time - but you can rest assure that you can use 100% linseed with excellent results, and I never seen the process documented with the usage of acetone. As for dichromate ? the answer is yes ? magnesium coated with dichromate has a long shelve life.

[mshaner]

Like BigG states, PD is the best method, but the risk are certainly present....I'm more comfortable with the linseed for now. If I had a real lab, then maybe the PD would make me less leary of the nasties.

Thank you very much for all your insight. This is a wonderful list.

Shane

[mshaner]

Regarding the coating with linseed. Is the a rule-of-thumb for how much linseed to Mg?

Shane

[BigG]

about 5%. I must warn you - first time you will do it - 5% will look very little - but don't be tempted to add more - you will get a clumpy mess.

[mshaner]

I would agree, the first time I did it this looked like a teaspoon of H20 in flour...I was really unsure as to whether I had read the information correctly and I still had a bit of green discoloration in one of my pyrogen mixes after a week or so.

Shane

[BigG]

The secret is to heat the metal gently and mix very very well for a few minutes. The whole metal needs to have a slightly different shade if all the particles are well mixed. Of course ? when mixing very fine powders ? you better to use hot plate.

[dfk]

Also, the effects of the chemical are more addressed toward people who use this on regular bases. Touching your skin once will not have future replications.

You don't have to have first hand experience feeling the side effects of a chemical to know what it will do to you. In fact that's why they come with MSDS so you can PREVENT contact; as I did.

However ? this is a dangerous chemical. Generally, most amateurs that I work with tend to use linseed oil ? although Pot. Dichromate provides a better protection.

Linseed protects in most cases one big acceptation is protection from ammonium perchlorate where K2Cr2O7 is a must.