PPM Calculations

is an abbreviation for “parts per million” calculations, which plays a pivotal role in exchange and recording of information relating to impurities in a substance. Impurities at a grosser level can be easily dealt with using percentages, which is a well known concept and is nothing but an acronym for “per hundred”. It may be noted that PPM calculations are usually with reference to mass unless expressed otherwise, while percentage expressions could be with reference to mass, volume or count that needs to be explicitly stated.
Utility of Ppm Calculations:

In many scientific experiments a very high degree of purity is required for reactants or substances used. Expressing purities in terms of percentage is no doubt possible in such cases but such expressions become lengthy decimals. This difficulty must have led scientists and mathematicians to devise calculations in terms of PPM, i.e. parts per million. In case of still lower levels of impurities concepts of PPB (parts per billion) or PPT (parts per trillion) are used.

It needs no explanation that it is much easier to say and understand 1 PPM than saying and understanding 0.0001%. PPM calculations are particularly useful in case of environmental pollution since a large number of toxic pollutants become life threatening at barely detectible levels.
Ppm Calculation Formula:

The formula for parts per million is analogous to percent by mass, but is more convenient when there is only a small amount of other substance present in a mixture or solution. PPM is defined as the mass of the component in mixture or solution divided by the total mass of the solution multiplied by 106 (one million) as shown below.

Mass of impurity

Parts per million = ----------------------------------------   X 106

Mass of mixture or solution

PPM value can be easily converted to percent mass by multiplying it by 10,000. Similarly a percent mass value can be converted to parts per million through a division by 10,000.