The Collaborative International Dictionary
Photogen
Photogen \Pho"to*gen\, n. [Photo- + -gen.] (Chem.) A light hydrocarbon oil resembling kerosene. It is obtained by distilling coal, paraffin, etc., and is used as a lubricant, illuminant, etc. [Written also photogene.]
Wiktionary
photogen
n. (context chemistry English) A light hydrocarbon oil resembling kerosene, used as a lubricant, illuminant, etc.