Question

define parts per million

Answer 1

HEY MATE_____>

In Science and  engineering, the parts-per notation is a set of pseudo-units to describe small values of miscellaneous dimensionless quantities, e.g. mole fraction or mass fraction. Since these fractions are quantity-per-quantity measures, they are pure numbers with no associated units of measurement.

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Answer 2

Just as per cent means out of a hundred, so parts per million or ppm means out of a million. 
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