Fenske, formula

This formula has the advantage with respect to those of Rose that it can be used with arbitrary values of Xb and %, though only with v = 00. The Fenske formula has been converted by Melpolder and Headington [90] into a nomogram, by means of which the data required can be found quickly and easily (Fig. 76). In the nomogram the following example has been shown ... 

The minimal number of theoretical separation stages which is required for the crude argon column to accomplish the O2—Ar separation, is estimated with the Fenske formula. This formula holds for infinite reflux, L/ V 1. This condition is almost fulfilled since typically only 1 part out of 30 parts of ascending vapour is withdrawn as crude argon from the top of the crude argon column, whereas 29 parts of liquid remain as reflux. 

Procedure Using a magnetic stirrer, dissolve 300 mg of sample in 200 mL of Tetrasodium Pyrophosphate Solution. When solution is complete, or after 30 min, whichever occurs first, transfer 10 mL of the solution into an Ostwald-Fenske viscometer, and determine the time, / , in seconds, required for the liquid to flow from the upper to the lower mark in the capillary tube. Calculate the viscosity, in centipoises, by the formula... 

Procedure Determine the flow time, in seconds, of the solvent (to) and of the three Sample Solutions (ti, t2, and t3, respectively) in a Cannon-Fenske viscometer immersed in a constant-temperature bath maintained at 130°. Calculate the specific viscosity, T sp, of each Sample Solution by the formula... 

By taking logarithms of both sides of this formula, we obtain the Fenske equation [155] for determining the minimum number of separating stages (see section 5.1.4.2) in a batch distillation of an ideal mixture ... 

Reed and Fenske [228] have evolved a formula for calculating the pressure drop in packed cohmms which is given by Brauer [208] in this form ... 

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