Grasping Solution

Basically, grasping solution is a liquid which spontaneously generates disembodied human arms. First appearing some time around the year 400, the exact origins of this substance are lost to history. Much like the rest of the world, alchemists have no idea why it does this. Unlike everybody else, rather than trying to destroy the clear abomination against nature, they've figured out how to utilize its odd properties.
Arms are only generated when the liquid's exposed surface area is great enough for at least one arm to reach through, so it can be stored in bottles without triggering the effect. However, any continuous mass of grasping solution with a volume greater than exactly 100ml will vanish. Because this always occurs at exactly 100ml, grasping solution is commonly used to calibrate measuring devices.
Grasping solution converts any blood that it comes in contact with into more of itself. It's about twice as dense as blood, but consumes ten times the equivalent volume to create more of itself- it's unclear where the other 80% of disappearing mass goes to. A small amount of grasping solution is seen as a part of every accredited alchemist's standard toolkit, fed as needed. In some ways, it's vaguely analogous to a baker's starter. Running out is seen as incredibly bad form- a sign of carelessness and disrespect for the craft.
While it ordinarily fails to mix with other liquids, blood can act as a sort of intermediary. This makes it great for removing stains- just splash blood on the stained object, then apply solution to mop it all up. However, it has a tendency to also pick up whatever dyes are embedded in the material, making it less than ideal for more vibrant cloth. By the same token, it can be used for sterilizing equipment.
A significant portion of Eidel's reputation for excellent doctors can likely be chalked up to the practice of using the arms generated by this solution as test subjects for localized treatments.
Some religious sects, particularly to the southern provinces, utilize grasping solution in the annual harvest festival's blood sacrifices. This isn't officially sanctioned, due to the fact that nobody's sure where the blood vanishes to when it does- while likely, there's no guarantee it actually goes to the goddess if sacrificed in this way.
Despite seeing common use, nobody has managed to figure out why it behaves the way that it does- in particular, where the arms come from.