MB125 processor & PCB

[ander]

I suppose isopropyl alcohol can only oxidize to acetone, therefore seems much safer to ethyl. It should not create fulminuric acid- very specific conditions are needed- based on my own experience. And I stay away from this since accident. I often use organic water miscible solvents to rinse powders- except well adsorbing ones.

 

[butcher]

the only place I use rubbing alcohol was during inceneration, dampening powders to keep torch from blowing away fine powder.

Harold do you see a danger there?

 

[Oz]

Perhaps I am missing something here but if you are using an alcohol to dampen material so it does not blow away from torch gasses why not use water? Not that I want any liquid with my metals when I go to melt them, as I go out of my way to be sure they are dry.

There is less of an explosion worry with water (water to steam is a 40,000 times expansion in volume though) but at least it is not combustible. Water will also keep your material wet to a higher temperature than alcohols.

I would suggest concentrating on the gradual heating of powdered metals with low pressure gas than trying to wet them.

 

[ander]

I think we completely misanderstood each other. I use alcohol for faster drying of material. Water has very high heat of vaporization, alcohol evaporates easiely and at lower temperature. Explosion hazard is unlikely due to open air processing. Each gas/vapor has specific limits of concentration in air within it's explosive. Below and above these limits mixture will not catch fire at standard conditions. Usually I use electric plate and pan to dry alcohol moisted powders. It is also possible to use furnance and open flame to dry powders, just fire up the powder then heat it up- Powder will not oxidize until is wetted with alcohol and after that until is heated to its spontaneous combustion temperature. The problem may be with exploding grains of methal with trapped alcohol. Personally I had no problem with that- just mixed from time to time. Exploding or "cracking" is phenomena one could meet in rotary evaporators at very low pressure salt drying- I personally witnessed 3 or 4 batches of certain salt making that scary sound.

 

[ander]

I finally got some gold. I oxidized metals with sodium persulfate, nickel went into solution. Then I dissolved tin and lead with hydroxide and put the rest containing copper oxide and gold into hydrochloric acid. I got black powder which was washed and after all I got tiny amount of gold, not worthy an effort.