108
3 Traceability: Reference Materials
BASE STANDARD (51)
CHEMICAL STANDARDS
ANALYTICAL STANDARDS
I
Primary
I
I Secondary I
\
J
Fig. 3.4. General types of standards used in chemical metrology and traceability among
them. Traceability between each standard and the next is realized through the intervening
zone (interface)
Box 3.S
Physical measurements are also amenable to ranking in a manner similar - though not
identical - to chemical measurements (see Fig, 3.S).Thus, the last link in the traceability chain
for mass measurements is the kilogram prototype, which is kept by the International Bureau
of Weights and Measures (BIPM) near Paris. The next standard type, the kilogram primary
Kg Prototype
BIPM
Kg primary standard
National metrological bodies
First·class transfer
weights
Second-class transfer
weights
r-------------l
1
1
1
I
1.._------______ 1