Chemistry question

I have been trying to search on this and am not coming up with useful stuff, so I’m hoping the vast hive mind of the internet can help out.

In my story, “The Bride Replete,” I have an alien race which uses some of the members as repletes to store large quantities of food in their crops (a sort of sac for, well, food-storage). I had thought of using sodium bicarbonate and water to create a constant pressure in a replete’s crop during the process of stretching them. Would this work? They do have a sphincter they can close and open voluntarily. Is there something better?

Many thanks!

Edited to add: This is a totally alien planet with no human interactions, so brand name things are right out. The technology is roughly equivalent to mid-1800s England, though there’s room to play, since it’s another planet.

Edited further to add: This is an artificial process to speed up the way it would work naturally. It’s someone using science to do what would naturally happen by just eating more food everyday. This is a way to prep a new replete for when the harvest season begins.

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7 Responses

  1. Mary Robinette Kowal

    Dad: I had the same thought, but have two problems. 1) Where would my aliens get Mentos and diet coke? 2) That reaction is caused by the carbonation in the soda interacting with the surface of the mentos. I need something that will create the carbon dioxide, or some other similar gas.

  2. -d-

    What! They are not invading earth?

    Sodium bicarbonate and vinagar makes CO2

    You could use something like sugar and yeast and let it ferment in their stomach if they don’t digest sugars normally and the acid in their stomach isn’t strong enough to kill the yeast. Then they would be drunk as an added bonus.

    Anything that makes you belch is because of gas buildup in your stomach. A carbonated drink at just the right temperature to hold the most CO2 would work as well as Mentos and be a lot less violent. This is going to be mighty uncomfortable.

  3. Mike

    Vinegar is naturally occurring in a number of species. Mix it with ground up limestone and you get CO2, or mix it with sodium bicarbonate, as you prefer.

  4. onlyocelot

    Does it have to be chemically-produced pressure? If they’re alien, why not an air-pump arrangement: between throat and crop, add a second sac. It could be between throat and sac, acting as guardian and regulator for air and nutrition-fluid flow, or between lungs (if your aliens have ’em) or external port, if it moves only air.

    To fill and stretch the sac, open the throat/lung/port sphincter (input sphincter for short, this is getting unweildy!) and expand the sac. Close the input sphincter, apply muscular pressure and open the sac-crop sphincter to push air into the crop. To relieve pressure, open both sphincters at once.

    To allow retaining fluids while letting air out, place the input sphincter at the bottom of the sac, and the crop-sphincter at the top of the crop. That way, gravity keeps fluids away from the sphincters when the aliens are right-side up, and they can vent air at will. If they get inverted and have to vent, the crop can use peristalsis to mix air with the nutrient, the crop sphincter opens to allow some into the sac, then the sac muscles expand the sac to reduce pressure and draw the air out of the mix. This is vented from the input sphincter, which is now “on top”, until nutrient is all that’s left, and the nutrient is returned to the crop.

    A bit complicated, but it would work.

    I really do worry about chemical reactions being used to maintain pressure in a living body without some pretty impressive (and hard to justify) evolutionary miracles. What happens if you use an acid (vinegar, stomach acid, etc.) and limestone mix, and you get a chunk of limestone that is 95% pure? way too much pressure. And if you get a chunk that’s only 5% pure, you’re not going to get much gas from it at all. (and the grinding can be a bummer!)

    With the 2-port sac, the sphincters need nerves that sense pressure and the presence of fluid, the crop needs to be able to slosh the nutrient and the brain/ganglia need to sense position, all of which have happened on earth by natural means. Plus, you don’t run the risk of a flesh-pump creating more pressure than a flesh sphincter can contain!

    Just my thoughts on the matter.

    ray

  5. Mary Robinette Kowal

    Ray: Wow. That’s a wonderful breakdown of how things could work. Thank you! I may incorporate some of that anyway. I’ve gone back and edited my original post to explain that this is an artificial process intended to accelerate the natural way things would work.

    Normally the crop would get stretched by simply eating a little more everyday. But we’ve got someone who is using science to speed things up.

  6. -d-

    You know how we don’t throw rice at weddings any more because birds were eating the rice and it swelled up inside them and killed them or at least did something very bad to them? How about swelling the crop the same way except on purpose?

    Calcium carbonate (carbide) produces acetylene when it reacts with water. Folk legend (as opposed to urban legend) has kids feeding carbide to chickens to watch them blow up (from the expansion of the gas, not an explosion). Acetylene is explosive at any concentration so would be very dangerous except there would be no source of ignition in the crop. When the gas is expelled is another story altogether. Remember the Bud Lite commercial with the horse and the candle during the Super Bowl a few years ago? Of course that was methane instead of acetylene.