Conversion from One Standard to Another

To convert a 8 value referenced to a given standard (1), to its value when referenced to another (2) multiply by the factor y, 

The 8 values are, of course, expressed in per mil (%o). The result is approximately the same as that given by, 

Similarly the fractionation between two samples, say A and B, both referenced to the same standard is, 

Defining Aa=b = 8B — 8A we arrive at the simple and very useful result 

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