You'll wonder where the yellow went when you brush your teeth with Pepsodent
An early TV advertising slogan for Pepsodent toothpaste, in use in the USA and UK from the late 1940s to 1960s.
The product purported to contain a product called I.M.P. which, it was claimed, 'cleans the stains and film away' and Irium, which 'fights tooth decay'. It would be difficult to get away with such claims in today's more regulated media environment. The mysterious I.M.P. wasn't specified and Irium was pure invention - there's no such chemical.
The product's manufacturers ran a television advertising campaign for 'New Formula Pepsodent', featuring the 'You'll wonder where the yellow went' jingle from 1948 onwards.
By the 1950s the company appeared to lose faith with the slogan and they ran a newspaper competition in 1956 in the USA for readers to write a new jingle. They must have been serious as the prizes included a 10-day all-expenses air trip for two, two Jaguar XK-140 sports cars and two mink coats. They needed have bothered. The line is still well-remembered by many and is probably the only reason that the product's name is still known.
Pepsodent is still on the market (2006).