【評論主題】47.下列有關Fisher subsieve sizer之敘述，何者錯誤？(A)可用來測定粉末之表面積(B)是利用空氣受電離子化之原理(C)空氣進入樣本前宜恆壓(D)空氣進入樣本前宜除濕

【評論內容】

A fisher sub sieve sizer uses air permeability method to measure the surface area of powders. But it does not stop at surface area. Calculated by equation, we got average particle size of such powder. A) is right, B) is wrong, cause it uses air permeability mehtod, C) is right  casue by such principle a constant air pressure is a must, i.e. 50 cm water pressure, D) is also right cause before passing through the compact sample zone, the air must be dried by drier. Such machine is first made by Fisher Scientific in USA and now the most popular fisher sub sieve sizer is HMK-22 Fisher Sub Sieve S...