Full Metal Alchemist 2003- Sloth’s Death
While it is largely overlooked and somewhat forgotten, there was an earlier adaptation of Hiromi Arakawa’s world-famous manga Full Metal Alchemist. In 2003, 2 years after she began writing Full Metal Alchemist, it was adapted into a 51-episode TV series with a movie sequel. The anime was well liked at the time despite having an anime original ending, as the manga wouldn’t end until seven years later in 2010. In 2009 a second anime adaptation of the manga was made called Full Metal Alchemist Brotherhood, which was a complete adaptation of the entire manga, and is now seen as the superior adaptation of the manga. While I do agree with this sentiment, the 2003 series does have its charm despite how it deviates greatly from the original manga.
Sloth is a villain in both series, but the two incarnations couldn’t be more different. In the original story, Sloth has the appearance of a very large man, who constantly complains about having to do any work. This stays true to his being named after one of the seven deadly sins, namely sloth.
Due to the manga still being ongoing, Sloth from the 2003 anime couldn’t be more different. In this case she does not have any connection to the deadly sin.
In addition to looking nothing like the original sloth, the sloth from the 2003 anime has another key difference. In the 2003 anime she might look like a human woman, but she is actually made of water.
Why does this matter?
The fact that the 2003 Sloth is made of water is actually a key plot point that allows Edward Elric to defeat her. As I have previously discussed, the alchemists in the world of Full Metal Alchemist can break down chemical compounds and reform them into other chemical compounds. Edward uses this skill to convert Sloth’s entire body into another compound, specifically ethanol.
When Edward changed Sloth’s water body to a body made of ethanol, he was taking advantage of a chemical property called vapor pressure. The technical definition of vapor pressure is:
The pressure exerted by a vapor in thermodynamic equilibrium with its condensed phases at a given temperature in a closed system.
Here is a simplified version: the vapor pressure of a substance tells you how volatile a substance is, which means how quickly it will evaporate. The higher the pressure, the faster it will evaporate, and the lower the pressure, the slower it will evaporate.
Water (H20)- 3.17 kilopascals
Ethanol (CH3CH2OH)- 5.95 kilopascals
Essentially Edward increased the rate at which Sloth evaporates by 47%, which would be a serious problem to a creature made entirely of water.
Now this scene does make sense if we are watching someone made of a highly volatile compound evaporate, but it’s happening a bit too fast for a body that is now made of ethanol, as ethanol is not an extremely volatile compound. There are a number of more volatile compounds but those compounds can be more complex, and would probably slow down the speed at which he converted Sloth’s body. There are a few that have a similar structure to ethanol, but have a higher vapor pressure.
Methanol (CH3OH)- 13.02 kilopascals
Acetone ((CH3)2CO)- 30.6 kilopascals
These compounds would have sped up Sloth’s evaporation by 219% and 514%, respectively. This would have dramatically sped up Sloth’s evaporation, but not to the speed we see in the anime. Also, methanol is a smaller simpler compound than ethanol.
While acetone is more complex.
The basic chemistry and concept behind Sloth’s death is sound, if a little exaggerated. However, Full Metal Alchemist is essentially using alchemy for magic. Seeing that people made completely of water don’t exist in the real world, I can’t call this one busted, confirmed, or plausible, but it is an interesting use of a chemistry concept in anime.