Formula 14 are pills that was featured in Land of Black Gold and used to sabotage Speedol Oil's oil supply. They caused the petroleum to blow up, which destroyed the engines of cars which contained the sabotaged oil. Used, and maybe invented by Müller.
In the Land of Black Gold, Thomson and Thompson swallowed some, mistaking them for aspirins. The pills caused their hair and beard to grow extraordinarily long, changing color every minute or so. It also gave them the hiccups, accompanied by burping up green bubbles. The condition returned in Destination Moon, when Captain Haddock had to cut their hair continuously. Professor Cuthbert Calculus created an antidote for Formula 14, although in the process he almost blew up Marlinspike Hall. Other professors had tried, during which the lab of one had been blown up. The mysterious explosions of the oil sparked the interest of many, including Tintin, who eventually obtained them from Muller.