The word phlogistons is playable in Words With Friends™, no blanks required. Because it is longer than 7 letters, you would have to play off an existing word or do it in several moves.
Words With Friends™ Letter Score: 20
Highest Scoring Words With Friends™ Play In The Letters phlogistons
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Seven Letter Word Alert: (38 words)
goosish, hooping, hooting, hosting, isogons, longish, looping, loosing, looting, losings, lotions, ooliths, options, photons, pistols, pistons, plights, plosion, poisons, poohing, pooling, postils, posting, potions, shooing, siphons, slights, sloping, soloing, soloist, sooting, spigots, splints, stonish, tonsils, tooling, topsoil, tossing