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Name: LoraLea
Status: other
Grade: other
Location: TX
Country: N/A
Date: December 2006

Question:
As a child my mother put mothball into a tall cylinder filled with water and set that cylinder on a coffee can with a light inside it. She would add a substance(s)...either baking soda or boric acid and maybe vinegar. The moth balls would rise and fall at various intervals and was beautiful to look at ...similar to the Lava Lamps that you see in the stores today. My search is to find the formula for the Dancing Moth Balls. Water + Vinegar + baking soda + or boric acid. I have searched the Internet and found Circulation Moth Balls, but no formula or recipe for making that same experiment. I am looking for exact proportions. I would love to do this for my grandchildren because it was such a beautiful memory for me. The heat from the light bulb may be necessary for the moth balls to rise and fall or it may have been a pretty addition to the colored water Mother used. Thank you for your time in researching this and your assistance especially during this very busy Holiday season. If you have an answer you will make eight families plus generations to come very happy.



Replies:
LoraLea,

The "dancing mothballs" effect is really the result of bubbles forming on the underside of the mothballs causing it to be lifted to the surface. At the surface, the mothballs tend to roll around and the bubbles are released, causing the mothballs to sink back to the bottom. As such, the mothballs do not have to be used. I have seen the same effect replicated using raisins or sultanas - this is probably safer since some people have an allergic reaction to the naphthalene in mothballs, and raisins do not have that mothball smell.

The trick then is to develop bubbles at a regular and slow basis. This is often accomplished by placing vinegar in a tall, thin vessel, adding the raisins (which should sink) and slowly adding baking soda to the vinegar mixture. The reaction of the vinegar and the baking soda will produce carbon dioxide which will buoy up the raisins. Since the initial reaction is strong, the raisins will be buoyed up pretty fast. However, when the reaction subsides, the production of bubbles diminish, the raisins sink - until more gas bubbles are trapped on the underside of the raisins to once again buoy them up.

Thus, the "recipe" calls for vinegar and the slow addition of baking soda (and further slow addition when the rising and falling of the raisins subsides). There will come a time when the acetic acid in the vinegar will all have been consumed and the liquid will have to be replaced - you will note that further addition of baking soda does not cause any more bubbling.

Since bubble formation is the key, I imagine plain water and AlkaSeltzer (which is nothing more than some analgesic in baking soda and citric acid) will work just as well, and may have the added advantage that one could just drop a tablet in a tall cylinder of water.

Have fun!

Greg (Roberto Gregorius)


LoraLea-

The mothballs now are para-dichloro-benzene, but they don't work because they are 30% heavier than water, and the bubbles are not strong enough float them up. Old mothballs were naphthalene; they work but are hard to find now. Some places well outside cities still have them. Naphthalene is only ~3% heavier than water, so it lightly tries to sink until some bubbles stick to it and push it upwards. When it gets to the top, the bubbles pop off, and it sinks again.

Making some bubbles does not need heat, just baking soda and enough of any acid (vinegar or boric acid). So your lamp is just for looks, which is of course what it is all for... I suspect you really _do not_ want the whole thing to get warm, because it might emit a much stronger mothball smell. so feel free to put ventilation holes at top and bottom of your lamp-cylinder, and a window-glass across the top.

Maybe I will try to figure out a way to make water 30% heavier, so the ParaDichloroBenzene mothballs will work. Some unusually heavy salt...

It is also possible some crafts person will make similar-looking balls out of grains of some translucent wax and/or plastic, with density adjusted to match water, and then we'll be back in business, sort-of. You are the second letter I have had about this.

Jim Swenson



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