Fluorinated gases pharmaceutical industries, as well as in refrigeration when combined with other gases. PFCs were commonly used as fire extinguishants in the past and are still found in older fire protection systems. They are also a by-product of the aluminium smelting process. Sulphur hexafluoride (SF) is used primarily as an insulation gas. It can be found in high-voltage switchgear and is used in the production of magnesium. HFCs were developed in the 1990s to substitute substances such as chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs). As these substances were found to deplete the ozone layer, the Montreal Protocol lays down provisions for them
Radium, and other radioactive substances red glass windows while the disease went through certain stages. Radium, and other radioactive substances Radium, and Other Radio-active Substances; Polonium, Actinium, and Thorium is a book published in 1903 by William Joseph Hammer, when he was about 50 years old. The book is the text of a lecture delivered at a meeting of the American Institute of Electrical Engineers. The title of the lecture was "Radium and other radioactive substances with a consideration of phosphorescent and fluorescent substances. The properties and applications of selenium and the treatment of disease by the ultra violet light". The lecture was augmented by