Accuracy

The high degree of accuracy attainable in some branches of chemistry and physics is out of the question where evaluation of specific surface from adsorption data is concerned. Even in the favorable case of nitrogen or argon, a divergence of at least ±10% from the actual area of the solid should be expected (owing to theoretical factors not yet supported by accurate quantitative assessments). In addition, there are several nonnegligible experimental uncertainties, which can be strikingly illustrated by results of a round-robin test. The project embraced thirteen laboratories, all well experienced in the field (Ref 10). The participants determined detailed isotherms of nitrogen (often 30 to 40 points), calculating both the specific surface, based on am (N2) = 16.2 A2 and the value of the BET C-parameter.

Solid

Surface area and

No. of

standard deviation, m2/g

labs

Graphitized carbon (Vulcan 3G-2700)

71.3±2.7

6

Graphitized carbon (Sterling FT-2700)

11.00±0.8

5

Plasma produced silica (TK 800)

165.8±2.1

4

Mesoporous silica gel (Gasil (1))

286.2±3.5

3

0 0

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