what is Potassium Cyanide

never heard of it...

https://en.wikipedia.org/wiki/Potassium_cyanide

It's not a drug; it's a poison. It kills people.

Potassium cyanide is a chemical compound - KCN. It is toxic, some famous people have been killed or committed suicide using this chemical.

It has industrial uses. I have never heard of this being used as a drug.

besides being among the deadliest of poisons (second to compound 1080) its a very useful molcule. In my field, when gold mining was no longer a"just pan for the big nuggets or even the dust, it was found that gold was tied up in hydroochem complexes of tiny molecules in rocks like quartz or serpentine and even anthracite coal and igneous iron ores.
A guy name of Elsner, a street wise chemist, discovered the euation hich several other guys made into a pprocess. if Theybroke up the big rocks and floated em in a mixture of KCN and water into which they blew air bubbles to make a froth. The gold would form another molecule called Potassium Cyanaurate. Its basically a molecule thats the product of a muti step redox reaction(Elsners discovery). The air bubbles would take the gold up into solution with the ionized KCN and this resultant molecule could be coaxed to "mine out" individual gold atoms within the rock (IF) the rock sizes were small enough. If you live in Colorado near Pikes peak, they still do a lot of mining using this pocess. They will crush what they know is the gold ore (They assay the rock from drill hole samples) and then, if the gold is greater than about .05 oz gold p ton . They will make these great piles of crushed ore and lay it on top of specially created plastic lined slightly pitched beds and then they start spraying the water mix of KCN over top of the pile. The air starts the reaction(which os named after our chemist friend) and after a few hours or days or weeks, the gold gets washedd in the flush water and it colleted and reacted and the "heap of rocks" Is gone over with like a big tool on a xherry picker which crushes the rock a bit more and then restrts the cyanide leaching . This can go on for months an the area around a gold heap can smell like almonds.
We use to wear Class 2 masks with a cyanide "pot" that screws into the filter holders (They had cute names for the filtr holders but it is rather coarse).

Most gold mining is done this way today.(Some is done with rock dust in a foamy slurry of KCN, but this is really expensive ) Very little gold except for that we see on "Alaska Gold Shows" is mined just panning or washing.
Im amazed I havent been gassed like Charlie Starkweather since Ive spent lots a time in the gold fields of US,Argentina, Brazil, and the Phillipines. Weve always had our share of industrial accidents with this stuff and it was usually from the macho douhe bags who didnt wear their safety gear and wound up nearly killing themselves with KCN induced cardio incidents.

There are some neat violent reactions we'd induce in chem labs using KCN and a few other ingredients. Ca (CN2) is dealy but muh cheaper molecule to make and it does some of the same stuff in gold mining