Teacher slashes student in 'bloody' experiment

This viral video appears to show a Russian teacher slicing up a student's arm with a knife — but the gruesome effect is actually all down to the miracle of science.

After daubing the student's forearm with a wet ball of cotton wool, the teacher cuts into the girl with the blade and leaves behind several oozing red gashes.

But luckily, it's not blood: a commenter on Reddit, where the video was posted, claimed that the teacher has merely chosen a dramatic way to demonstrate a straightforward chemical reaction.

"Skin was rubbed with a cotton ball soaked with a solution of thiocyanate ions, and that knife was covered with a solution from of iron(III), which has yellowish colour," the commenter explained.

"When solutions have combined, these ions reacted together, forming blood red."