Neodymium acetate

• ... that neodymium acetate (pictured) can be used as a substitute for uranyl acetate?
• ... that praseodymium means "green twin" in Ancient Greek?
• ... that an altostratus cloud can be formed of water droplets, ice crystals or both?

June 30

Tower Bridge in 2009

• 1894 – Tower Bridge (pictured), a combined bascule and suspension bridge over the River Thames in London, was inaugurated.
• 1934 – German chancellor Adolf Hitler began a purge of the paramilitary wing of the Nazi Party and other political rivals, executing at least 85 people.
• 1974 – Municipal workers in Baltimore, Maryland, went on strike seeking higher wages and better conditions.
• 1985 – Ryan White, an HIV/AIDS patient in the U.S., was denied re-admission to his school after he had contracted the disease from hemophilia treatments.