# Baking Soda and Vinegar: Are there any secondary reactions?

I want to run a Lego Pneumatic Engine on the CO2 that is produced, but before I do, I want to be sure that that's the ONLY gaseous product from a real-world reaction. Everyone seems to assume that it is, just by omission, but no one actually says it.

I'm sure it would run, but I'd rather not damage the ABS plastic or probably-steel parts (shiny metal piston shaft), or a rubber seal or the factory lubricant or something else that I can't see. CO2 seems inert enough by itself, but is that really ALL I'll get?
(assuming of course, that I keep the foam out)

• Vinegar contains about 50 - 60 g acetic acid per liter. The other acids are tantric acids and lactic acid, which are present at 1 to 3 g/L. All acids react with baking soda with production of $\ce{CO_2}$ No other substances can produce a gas, with reaction with baking soda. – Maurice May 29 '20 at 9:53
• You won't get pure $\ce{CO2}$ out of an aqueous solution. There will be water vapor in the $\ce{CO2}$. Over a period of time that will almost certainly cause any steel Lego parts to corrode. – MaxW May 29 '20 at 10:17
• @MaxW That makes sense. If there's water involved, then inevitably some will evaporate. So how does that compare to normal humidity? These parts are about 20 years old, with no special care except possibly by accident (open air and regular use for the first 10 years or so, then in sealed plastic bags for maybe another 10 years, all climate-controlled), and no discernible damage so far. – AaronD May 29 '20 at 10:54
• Acetic acid and dissolved salts will promote corrosion, unless it is stainless steel. And even in that case, the shiny polished surface may got not so shiny over time. – Poutnik May 29 '20 at 15:12
• So far, the biggest concern seems to be the metal shaft. Plastic, rubber, and a bit of grease are all okay by omission then? – AaronD May 29 '20 at 18:12