Thanks Nerd_Weed and Glenn!!
Yes, I actually have 2 bubblers built, using 1-gal. windshield-washer fluid jugs. I have been cautioned and scared enough by everyone's posts!!
I am just not sure why I would need more than one bubbler, tho. ...and I've seen pics of THREE bubblers in series.

Does the 'gas' become changed after passing through more than one bubbler? Does it change after passing through just ONE bubbler?

Is it possible for the gas to backup through just one bubbler??

...and is it okay to use plain tap water in the bubbler and in the gas-output measuring device, or should it be distilled water, like we are using in the call (for now)??
Thinking about 'bubblers' a bit just now brings to mind Bob Boyce's version made from a water filter housing, compared to Chris' and other bubblers I've seen around 'town' here.

Is the bubbler subject to possible
explosion from a back-flash?

SHOULD the bubbler be constructed from PVC or ABS or something stronger than a soda bottle?
I have the exit-tube coming out through the cap of the plastic jug.

Would it be safer/better to have it come out near the neck of the jug and leave the cap as is?
is of UTMOST importance! Who wants to get blown up before making a great-working cell? LOL