The distribution of this quantity is inferred from the shape of a type IV isotherm in the Barrett-Joyner-Halenda method. Materials with a “controlled” value of this quantity serve as solid supports for oligo·nucleotide synthesis. When expressed (15[1])in a non-SI unit, a series of 3 materials with a “type A” structure have values of this quantity equal to 3, 4, or 5, depending on whether they have potassium, sodium, or calcium ions. In a typical SI unit, whether this quantity is less than 2, between 2 and 50, or greater than 50 determines if the material is described with the prefix (-5[1])(*) “micro,” “macro,” or “meso.” Beads with a fixed, small value (-5[1])of this quantity are used to separate proteins in size-exclusion (-5[1])chromatography. For 10 points, zeolite-based molecular sieves have values as low as 3 Angstroms for what (10[1])quantity which characterizes the holes in a material? ■END■ (10[3])