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Recently, I came across a video and a news report where it has been reported that a man from India has invented a car which uses water as a key fuel component. The car runs on acetylene gas produced by the reaction of water and calcium carbide in the car's fuel tank. The source of the video is this post off Facebook from History TV18.

The claims are too good to be true and I doubt them. However, I do not know much about cars, automobile/mechanical engineering, and chemistry to check the veracity of the claims. How legitimate are the claims? Do they hold any merit?

Oddthinking
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Janus Boffin
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2 Answers2

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The car does not run on water. The article you link says quite clearly that "The car runs on acetylene gas".

Acetylene is an explosive gas that is used for welding, and before the invention of electric lamps it was used for lighting. It is produced from the reaction of calcium carbide and water, as follows:

CaC2 + 2H2O → Ca(OH)2 + C2H2

The problem is that, while water is cheap, CaC2 is not. It is normally made from methane - which would be a better and cheaper fuel. Converting it to Calcium Carbide is done by partial combustion, so some of the energy available in methane is lost.

For more information on acetylene, see the Wikipedia article.

Jan Hudec
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hdhondt
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    +1. Acetylene is what spelunkers' lamps used to use for fuel (and, for all I know, still may), so it's a very old technology and a very simple one. – Robusto Apr 11 '16 at 02:00
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    Actually I think actylene lamps came long after torches :-) – jamesqf Apr 11 '16 at 05:06
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    @jamesqf : in some English dialects, torch = flashlight – vsz Apr 11 '16 at 11:01
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    Saying that water is the "key fuel component" in this is a bit like claiming that water is the "key component" of nuclear fusion because it's where we get the Deuterium. :-D – DevSolar Apr 11 '16 at 11:02
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    @DevSolar *enriched* water. – Mindwin Remember Monica Apr 11 '16 at 13:03
  • @Mindwin: Think about that composite noun for a moment. "Enriched water". How do you *get* "enriched water" (a.k.a. "heavy water")? You can't magick another neutron into a hydrogen core. But you can have lots of hydrogen cores undergo a process that *existing* deuterium cores have a higher chance of getting through, giving you a water that is "richer" in deuterium. You still *start* with *normal* water. ;-) – DevSolar Apr 11 '16 at 13:06
  • @DevSolar same way as enriched uranium starts with normal uranium. =) My previous comment should be read more like something that came out of the marketing dept. – Mindwin Remember Monica Apr 11 '16 at 13:33
  • @Mindwin: Well, that's rich. ;-) – DevSolar Apr 11 '16 at 13:34
  • Unless they have a mining source of CaC2 – Joshua Apr 11 '16 at 15:24
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    Better analogy: Saying that this car runs on water is like saying that cars with gasoline engines run on oxygen. – Dennis Apr 11 '16 at 16:46
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    I think the most important claim made in the source is that the fuel costs 10..20 Rs/liter (compared to 70 for gasoline) - per liter of what (just the CaC2? Combined with water? The acetylene gas itself?), and whether a liter of whatever is being measured has comparable energy to a liter of gasoline (or comparable fuel per distance to a car with a gasoline engine) – Random832 Apr 11 '16 at 19:03
  • @Mindwin "enriched water" - you don't mean "dehydrated water"? See http://www.bernardfoods.com/foodservice/beverages/dehydatedwater.htm – hdhondt Apr 11 '16 at 23:14
  • @Random832: That's why I always prefer $/km over $/liter. $/km always measures the cost of using a vehicle regardless of the details of efficiency or energy density – slebetman Apr 12 '16 at 03:38
  • There may be a bit of a [safety issue](https://l.facebook.com/l.php?u=https%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3DN-Qp2Lvrliw&h=wAQFqCrKr). – tcrosley Apr 12 '16 at 06:48
  • @hdhondt no. See above comment. – Mindwin Remember Monica Apr 12 '16 at 11:58
  • @slebetman that doesn't help anyone figure out if something is technically feasible, only if it's economically feasible. Economic feasibility changes for each new circumstance/economy/consumer. Add to it practices like [loss-leading](https://en.wikipedia.org/wiki/Loss_leader), and I would prefer knowing the factors that actually matter (energy density), than a highly imperfect proxy. This is similar to saying "place A is a 3 hour drive, I don't know or care about kilometres". Or for that matter, "my elbow is the meter". – Milind R Apr 13 '16 at 14:20
  • @MilindR: Energy density is a very imperfect proxy for measuring cost (see Random832's comment on the primary claim). I'd rather measure cost directly with $/km – slebetman Apr 13 '16 at 17:15
  • @slebetman It's an imperfect proxy both ways. Unless you're limited in capacity to understand, or you _really_ don't care, why would you prefer $/km rather than $/L and km/L ? the latter enables you to calculate feasibility in many more circumstances. it's like having 3 data points instead of the function generating it. – Milind R Apr 13 '16 at 19:22
  • @MilindR: The claim specifically discusses fuel costs and that it's cheaper in terms of $/L which is misleading (especially since he's measuring litres of water, not acetylene gas generated, besides, 1L acetylene gas is less dense than 1L liquid petrol). $/km would directly compare costs and expose that the carbide+water thing as more expensive than petrol. Why I didn't mention $/L - because that's already in the claim, I don't need to repeat it. Why not km/L - because if you have $/km you can directly compare costs.. – slebetman Apr 13 '16 at 23:53
  • .. It's not that I don't see the use of other metrics. It's that people rarely compare $/km - which is a more useful metric for the layman – slebetman Apr 13 '16 at 23:54
  • I... think that Calcium Carbide has nothing to do with methane. Partial combustion of methane is used to prepare acetylene directly, without using Calcium Carbide. They are two completely separate ways of getting the same compound. – T. Sar May 26 '17 at 13:42
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Not much to add to the chemical/technical background already mentioned by hdhondt.

A carbide (or better an acetylene) motor for the use in vehicles was invented much earlier. The earliest reference (german) I've found is an article in „Mitteilungen des schweizerischen Azetylen-Vereins“, Heft 10 vom Oktober 1918 (Bulletin of the Suisse Acetylene-Company - Issue 10 October, 1918) which mentions experiments with a "light motor vehicle" (mileage ~35 pounds of calcium carbide/100 miles), a 6 hp motor cargoship and a motorcycle with a range of ~75 miles.

The linked article also mentions similar tests in Germany (pre-WW1) which weren't very "satisfactory".

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