Step 9: Aluminum and Lye

To make H2 lifting gas for this project, I used the following reaction:

2 Al + 2 NaOH + 2 H2O → 2 NaAlO2 + 3 H2

This exothermic reaction occurs when you mix NaOH (lye) solution with solid aluminum metal -- the lye strips off the oxides on the surface of the metal and lets the water react with the metal to produce hydrogen gas. A lot of heat is released in the process, and increased temperature increases the reaction rate, which leads to increased temperature, and so on...depending on the amount of water you put in the reaction vessel, things can get out of hand very fast. The first picture shows one of the reaction vessels  used immersed in an ice bath (which had melted by the time I took the picture).

As I mentioned previously, lye is a strong base and will burn you pretty badly if you let it. Wear gloves, and always set up one of these reactions in a place where nothing will be damaged if the vessel overflows.

If you have a beefy DC power supply and want to get your gas by electrolysis, go for it, but I think you'll find it hard to match the reaction rate and volume of gas produced by the aluminum-lye method.
You blimp looks awesome, only the code is without any doubt the most incomprehensible code I have ever seen! I can't make heads or tails from it. Could you explain the how te code works? I really like the 433 MHz set I got, but I haven't found a clear code that I can adapt to my homemade rover. <br> <br>Thom
Darn, I have been trying to figure out your code for quite some time, IT-IS-SO-SIMPLE, I have tried to use virtualwire but then I can't use the servo library (they hate each other). Thanks for sharing it!
when I first read the title I accidently read &quot;Hydrogen bomb.&quot;
Nice work on this project! I had the same 433 Rx Tx units and could never get them to communicate properly! Definitely one of the best troubleshooting sections I've read!
this soo reminds me of the hindenburg. tho to be fair, hydrogen had nothing to do with the explosion. zinc paint(?!) was the problem. <br>very cool project. <br>tho 433mhz might not be legal in USA, but even a toy car with arduino could work
You are my hero. I have tried filling a smaller blimp with hydrogen in the same way, but using only very small amounts of lye (five attempts with no success). I would love to build a setup like this some day, especially one using a hydrogen fuel cell for power. One question: does the water buffer remove any steam or water vapor from the hydrogen entering the envelope? I always worried about getting water in it. Thanks for a very informative 'ible.
You're right to be worried about water vapor. It will only be a problem if you let the reaction get too hot, which will make it start steaming or even boil if it gets out of hand. If you make sure it doesn't get more than a little warm ( I dunno, 75 deg F), the water vapor will be negligible. If you're really worried about it, you could try running the gas through a percolator to cool it down before it enters the envelope (meaning some of the vapor would condense out). The buffer I have is mainly to prevent any water in liquid form that bubbles up from getting close to the envelope. Don't give up on lye!
Awesome. Love the chemistry lab details and the troubleshooting section.

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