Aw, go float yourself.

As I unwrapped a bar of Ivory soap, I heard the advertisements of my childhood clearly in my head:  "It floats!" and especially, "99 and 44/100 percent pure!"

And I said to myself, “Pure what?” I never really gave it a thought.

Some casual research revealed the answer: it is pure soap. Huh?

That required a little further research as I know diddly about soap making. It seems that soap is made from an alkali (basically lye or potash) and a fat (animal or vegetable). Manufacturers often add substances or chemicals that affect the smell, color, consistency, or generality of it.

Proctor and Gamble did not do that, and to prove it (to whom, nobody seems to know), sometime in the 1890's somebody from P&G sent samples of their white soap to independent laboratories for analysis. One scientist’s report noted that the total sum of the impurities in the soap was 0.56%. Some enterprising P&G executive who could subtract got the bright idea to advertise its purity with the famous appellation, “99 and 44/100% pure.”

As for the floating, that's the result of whipping it full of air. Whether the air is hot or not, it is extremely appropriate for advertising purposes.