Re: Ammonia spark gap ?

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Original poster: "Dr. Duncan Cadd by way of Terry Fritz <twftesla-at-uswest-dot-net>" <dunckx-at-freeuk-dot-com>

Hi Luc!

>Time to time I saw post on Poulsen arc, tyratron, quench spark
>gap; gap using hydrogen for it's propriety of quenching fast. I
>know in the old time they use nitrogen in quench spark gap to
>prevented oxidation of the metal surface of the gap ( in reality
>they put air but the gap is seal and after a short period of time
>the oxygen is all combined with the metal and only nitrogen remain.


Unless, of course, the seals leak like mine ;-)

>They used gap in kerosene or alcohol vapor, city gas, etc. the
>goal is to dissociated the gas or vapor to have a substantial
>amount of hydrogen present at the gap ( hydrogen transfer heat
>really fast and have the characteristic of quenching fast and
>conduct fast: ideal for a spark gap ). But these material have a
>down side; the sub product is carbon ( and oxygen in the case of
>alcohol vapor ) the carbon finish by producing short.


Yes, this is a real nuisance.  I tried introducing methylated spirits,
margarine or vaseline into a small quenched gap and this is exactly
the effect they gave, though initially the quenching was good.  I
recall reading somewhere that with the correct mixture of vapours, the
carbon electrode in a Poulsen arc grew by carbon deposition at the
same rate that the arc eroded it, thereby removing the need for
adjustments.

>Today I had a flash; why not using ammonia ( NH3 ) when
>dissociated may be it only produced nitrogen and hydrogen ? The
>advantage of the hydrogen without the disadvantage of the carbon.
>I try to find reference about it for an hour on the web without
>success, is one of you know something related to that ? Or have
>an opinion on this.


Like the reverse of the Haber process!  It sounds like a good enough
idea to me, only better be sure you've got no leaks, good ventilation
etc round the gap when you're filling up from the cylinder.  If
something goes horribly wrong and you get a face-full of ammonia
believe me you'll know all about it (found that one out the hard way a
long, long time ago.  Not nice.)  Perhaps a safer and cheaper way,
since you won't need much ammonia, would be to heat household ammonia
solution gently and pass the vapour through a tube filled with silica
gel to dry it.

Dunckx
Geek#1113 (G-1)