Diethylene glycol (DEG) is an organic compound with the formula (HOCH2CH2)2O. It is a colorless, practically odorless, and hygroscopic liquid with a sweetish taste. It is a four carbon dimer of ethylene glycol. It is miscible in water, alcohol, ether, acetone, and ethylene glycol. DEG is a widely used solvent. It can be a contaminant in consumer products; this has resulted in numerous epidemics of poisoning since the early 20th century. Preparation DEG is produced by the partial hydrolysis of ethylene oxide. Depending on the conditions, varying amounts of DEG and related glycols are produced. The resulting product is two ethylene glycol molecules joined by an ether bond. "Diethylene glycol is derived as a co-product with ethylene glycol (MEG) and triethylene glycol. The industry generally operates to maximize MEG production. Ethylene glycol is by far the largest volume of the glycol products in a variety of applications. Availability of DEG will depend on demand for derivatives of the primary product, ethylene glycol, rather than on DEG market requirements." Structure of DEG and related polyols Diethylene glycol is one of several glycols derived from ethylene oxide. Glycols related to and coproduced with diethylene glycol and have the formula HOCH2CH2(OCH2CH2)nOH are: n = 0 ethylene glycol ("antifreeze"); monoethylene glycol MEG n = 1 DEG n = 2 triethylene glycol, TEG, or triglycol n = 3 tetraethylene glycol n = 4 pentaethylene glycol n > 4 polyethylene glycol These compounds are all hydrophilic, more so than most diols, by virtue of the ether functionality. Uses Diethylene glycol is used in the manufacture of saturated and unsaturated polyester resins, polyurethanes, and plasticizers. DEG is used as a building block in organic synthesis, e.g. of morpholine and 1,4-dioxane. It is a solvent for nitrocellulose, resins, dyes, oils, and other organic compounds. It is a humectant for tobacco, cork, printing ink, and glue. It is also a component in brake fluid, lubricants, wallpaper strippers, artificial fog and haze solutions, and heating/cooking fuel. In personal care products (e.g. skin cream and lotions, deodorants), DEG is often replaced by selected diethylene glycol ethers. A dilute solution of diethylene glycol can also be used as a cryoprotectant; however, ethylene glycol is much more commonly used. Most ethylene glycol antifreeze contains a few percent diethylene glycol, present as a byproduct of ethylene glycol production. Toxicology Despite the discovery of DEG's toxicity in 1937 and its involvement in mass poisonings around