Walt's meth recipe is a little different than most; he has a secret ingredient. Keep it on the down low, but he uses DAST.
DAST, (Diethylamino)sulfur trifluoride, also known as, N,N-Diethylaminosulfur trifluoride, (Diethylamino)sulfur trifluoride. The reagent was first developed in 1977 by W. J. Middleton and E. M. Bingham as a method for fluorination. Diethyl(trifluorosulfido)amine is a highly reactive fluorinating reagent that reacts well with alcohols, carbonyls, and acid-sensitive compounds. It is also known to be used as a catalyst in Friedel-Crafts acylation and the synthesis or rearrangements of alcohols to aldehydes. Because DAST is known to react violently with water, face shields and full-face respirators are necessary when handling the chemical. It has a molecular weight of 161.19 g/mol, a boiling point of 30-32 degrees celsius at 3 mmHG, and a density of 1.22g/mL. It appears in the form of a colorless oil. The reagent is a liquid and can be used with standard glassware.
Org. Synth. 1977, 57, 72.
