[dhowland]

 At one end of a 4 to 6 mm id round plastic tube (suitable for the chemical), will be Chlorine Dioxide usually in liquid form at room temperature, at atmospheric pressure.  My question is,  what is the relationship of time to that of gas mixing over a distance inside of 4 to 6 mm id tubing, when no outside pressure is applied to move gas though the tubing.  The length of the 4 to 6 mm id gas filled tubing is around 600 mm.  We want to periodically purge the inside length of the tube with dry air, and want to work out a good time interval for this dry air purging cycle.  We want to do this to keep the chemical vapor concentration low on the dry air pump side of the tube.  We are also considering any appropriate filter on the pump side, and your experience therewith will be greatly appreciated.  A ffilter may be useful in the event of an extended power failure.   Thanks.  David

In Summary:  A  4 to 6 mm diameter liquid ClO2 surface is exposed to a  4 to 6 mm id conduit filled with dry air.  What may be expected in terms of chemcial vapor concentration 600 mm, in still air, up the tube at 25 deg. C at Sea Level, in aproximate terms, say in 24 hours from the start.  

[curiouscat]

Using Ficks Law



t=24 hrs = 86400 sec.
x=600 mm = 60 cm

You'd have to estimate Diffusivity  of ClO2 in air. I'm assuming 0.1 cm2/sec.

Hence:

n/n₀=0.63

That is, your tube end conc. would be 63% of n0. n0 would be the equilibrium conc. of ClO2 at the liq. surface which you'd have to again estimate from vap. pr. etc.

Hope this helps.

For even more accuacy use:



Apparantly the Vap. Pr. is 101 kPa at 20 C. So quite close to atmospheric Pr (what's its BP?). I think this would mean your vapor conc. n0 is almost pure ClO2?