GDS AR Ua tae He Sle ars Rea En aed WAR Eo wl De ene | e.g 
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(the ge gives a French aged for the thermometer. 
This publication becomes useful in furnishing a method of reat ane 
efficiency of fractionating columns, which indeed, on its practical side, is” not s 
thoroughly built up as that of Friedrichs, but which however in the formulating, offer 
something new. The method consists in this, that in keeping up of a certain rapidity — 
of distillation (one drop per second) equal fractions are collected and examined. If one 
starts with a certain quantity of a normal mixture of benzene and toluene with Vo 2 
benzene and finds in the first half distillate a g. benzene and b g. faker! tS the” 
efficiency figure runs thus:— E = (a—b)/v. 
ee ek 4 
ad ea ar 2 
In cases of excellent efficiency the expression approximates to unity, in cases of poor 
efficiency, to zero. It is not applicable to all numerical relations, of which one 2 cant 
easily convince himself, but only for a 50 per cent. starting material. : 
The Hempel column is so modified by W. Elsner’), that polished and finely-etched i 
glass marbles (beads) of various sizes are placed above one another in layers. Probably 
the amount of liquid retained is smaller, but the raised price and the increased trouble 
both stand in no proportion thereto. Further, in Elsner’s construction, the uncontrollable — 
jacket cooling is replaced by a reflux condenser with cooling coil and filled with glass — 
beads. This is really completely correct, only a special distribution-spray seems quite 
superfluous with laboratory apparatus. 
Further, the following contributions on laboratory practice will have an interest . 
here. Houben?) alters the Erdmann’) process of vacuum distillation in an atmosphere 
of CO;, by using a receiver cooled with liquid air in such a manner, that he —as usual 
in vacuum distillations— uses a “boiling-capillary” but feeds this also with CO,. The 
author remarks that the attained high vacuum is in no way deteriorated by this. Since . 
the manometer is joined on next to the condensation apparatus and not to the distil- . 
lation flask itself, the conclusion is false, as may also be the statement of the pressure 4 
(0.12 mm. Hg). e 
E. Lenk has devised*) a fractionating flask provided with two fractionating columns _ 4 
for thee distillation of foaming liquids;. the lower is provided with an efficient reflux ~ 
condenser; the upper is joined to the receiver by a usual distillation tube; both can a 
be evacuated over a three-way tap. The condenser is turned on first. As a rule the > 
foaming ceases when real boiling begins, and one can reverse in the lisa! way, ands . 
further distil. | . 
A further improvement consists in the shortened manometer for vacuum distillation. 
H. T. Clarke®) proposes that a hook-formed capillary should be fused in the closed 
limb, as is used in exact barometers. By this means, the inrush of air and steam on a 
the one hand, and on the other hand the all too rapid falling of the mercury 0 a) 
disconnecting, probably leading to a shattering of the apparatus, could be avoided. — 
- In our previous Jieport’) we had placed in view the publication of experimental 
principles for’ measurement of pressure in vacuum distillations. In the meanw 
these works have appeared’). The problem was solved in two sections: — first th 
pressure conditions were tested in the part of the boiling apparatus from the up 
part of the boiling tube to the branch behind the receiver; and then the temiacea 
and pressure relations in the boiling tube itself. 
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1) Crem. Apparatur % (1920), 3; Chem. Zig. 44 (1920), 11. —~ *) Berl. Berichte 52 (1919), 1460. — 
36 (1903), 3456. — *) Chem. Ztg. 52 (1920), 330. — 5) Journ. Americ. chem. Soc. 42 (1920), 786. ker : 
1919, 96. — 7) C. v. Rechenberg and E. Brauer, Zeitschr. 7: physik. Chem. 95 (1920), 184. res 
