Originally Posted by
mr fantastic 1 ppm means 1 part per million parts.
Now note: 1,000 mg = 1 g and there's 1,000 g in 1 L. Therefore there's 1,000,000 mg in 1 L. So 1ppm means 1 mg in 1 L of water.
Therefore 0.7 ppm means 0.7 mg in 1 L of water.
Therefore 1.4 mg of flouride in 2 L of water.