Perforation plates definition

Oldershaw column. An all-glass perforated-plate column. The plates are sealed into a tube, each plate being equipped with a baffle to direct the flow of reflux liquid, and a raised outlet which maintains a definite liquid level on the plate and also serves as a drain on to the next lower plate [see Oldershaw Ind Eng Chem (Anal Ed) 11 265 1941]. 

Recently, Sameshima(24) has measured the rates of flow of various simple gases through a compact unglazed earthenware plate. The rates of flow definitely did not obey the Knudsen formula t = k JM, where t denotes the time required for the effusion at constant pressure of a volume F of a gas of molecular weight M, and where fc is a constant. On the other hand, the law t = k M was accurately obeyed when the gases effused through a platinum plate with a single orifice. For the earthenware plate Sameshima found a formula t = to apply. If the wall was very thin n approached zero, and the simple behaviour of the perforated platinum plate was found. If the wall was thick n approached unity and the equation became t = kij (ij denotes viscosity). 

---