gamma-Butyrolactone is an industrial solvent, and a common precursor for the drug GHB. An interesting note on this chemical, is that it can be taken alone, and the body will convert it into GHB. This is mostly not done due to the horrible taste and the fact that it cannot be mixed with water (or more specifically, water based drinks) to hide the taste.

After GHB was banned by the FDA, GBL was sold under the name "Blue Nitro". It is now a "watched chemical" in the United States.

Physical Properties taken from the GHB Synthesis FAQ by "Rhodium":

mol wt: 86.09 
mp: -43.53øC bp: 204øC 
CAS No: 96-48-0 
Flash point: 98øC 
Soly: miscible with water, soluble in methanol, ethanol, acetone, ether, benzene 
LD50: 1720 mg/kg (orally, mouse) 1540 mg/kg (orally, rat) 
Uses: Solvent, paint remover, capacitor electrolyte, intermediate 
Synonyms: GBL, BLO, butyrolactone, gamma-hydroxy butyric acid lactone, 1,2-butanolide,
              1,4-butanolide, 4-butanolide, 2-oxanolone, tetrahydro-2-furanone, dihydro-2(3H)-furanone.