Re: Need Ozone

["Tesla list" <tesla-at-pupman-dot-com>]

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

Hi Tom, Ed, Jeff, All!

>Same lack of resources - So I saturated a small amount of hot water
w/ salt
>i.e. ( .001%)
>sodium iodide an mixed it with starch - Nothing happened so I
thickened the
>solution w/ more
>starch nothing happened - Then I thin the solution w/ more sodium
iodide
>still nothing - Guess I
>need a more concentrated form of sodium iodide or blue paper for any
results.


You may be right as this is indeed very dilute iodide - incidentally,
you didn't mention that you'd exposed this solution to ozone but I
assume you soaked a bit of paper in it and hung it up near a working
coil.  The iodide/starch alone will do nothing.  It needs the presence
of ozone to liberate elemental iodine from the iodide by oxidation of
the iodide ion, as per Jeff's original posting.  Then you get the
intense coloration with starch.  If you have any tincture of iodine in
your household medicine chest or first aid kit you'll see what I mean.
That ought to give an instant dark blue/black colour with starch.

However, it may also be that the chloride ions or the anti-caking
agents in the salt are interfering with things, I seem to recall (from
inorganic chemistry a long time ago) that iodine can form a complex
with other halide ions.  If you do have some iodine tincture and you
do see the blue/black colour with starch, you might try spiking a
small quantity of tincture with salt solution and see if it still
works with the starch :-)  If it doesn't, you know what's going on!

But the test Jeff posted does work, I can dimly remember doing this
over 25 years ago.  Perhaps for this purpose you really do need pure
(99%+) sodium or potassium iodide.  I don't know what degree of
success you are likely to have if you go asking for say an ounce of
this from your local chemist's shop.  If you tell them it's being used
to monitor for toxic levels of ozone they may be sympathetic ("health
& safety" is a great moral bludgeon phrase, cunningly wielded you can
extract almost anything from anybody.)  Of course, if the O3 test
strips you found on the web are cheap enough, that's obviously the way
to go,  but you may be faced with the situation that one box of test
strips only costs pennies, but there's a minimum order of $100, one
can but try.

The other test used for ozone detection, though less sensitive and
less rapid than the above, was to stretch a very thin (paper thin)
piece of natural rubber tightly over a frame a couple of inches in
diameter and leave it where it would be exposed to the ozone.  O3
attacks the double bonds in the rubber to form molozonides and
ozonides plus their decomposition products, and it becomes at first
sticky, then very brittle and its transparency decreases, becoming
white and opaque, which effects are intensified when the bonds are
stressed.  Nitrogen oxides don't have this effect.  The thinner the
rubber film, the more sensitive this test is.  Before the invention of
direct reading ozone meters, this was used for occupational health and
atmospheric monitoring many years ago.

Dunckx