SCHLUNDT — DIELECTRIC CONSTANTS OF PURE SOLVENTS. 361 



ratus in order to test it thoroughly. The dielectric constants of 

 ethyl ether, chloroform, ethyl benzoate, salicylic aldehyde, ben- 

 zonitrile, and nitrobenzene were measured, and the' results ob- 

 tained agreed very well with those given by Drude. It is there- 

 fore entirely superfluous to again report the numerical results 

 obtained for these substances. 



Experimental Results. 



THE XITRILES. 



The dielectric constants of the following aliphatic nitriles 

 were measured: Hydrocyanic acid, acetonitrile, propionitrile, 

 butyronitrile, iso-propyl cyanide, valeronitrile, iso-butyl cyanide, 

 capronitrile, and ethylene cyanide. In the aromatic series, ben- 

 zonitrile, benzyl cyanide, ortho-toluonitrile, mandelic nitrile, 

 and a- and /?- naphthonitriles were measured. 



Hydrocyanic Acid. — The sample of hydrocyanic acid used was 

 prepared in the usual way by slowly adding a strong aqueous 

 solution of potassium cyanide to sulphuric acid of Sp. Gr. 1.25 

 in a retort connected with a reflux condenser kept at 30° C. 

 The gas was then dried at 30° C. by passing it through a series 

 of three large U tubes, kept at 30° C, and containing fused 

 calcium chloride. The gas was condensed in a tube provided 

 with glass stopcocks, suspended in a bath at 0°. A colorless 

 liquid was thus obtained which left no residue upon evapora- 

 tion. Some of the liquid was introduced into the cell adapted 

 for the measurement of liquids having a high dielectric constant. 

 The cell was securely stoppered and the measurements were 

 made at 21° C. jSTo appreciable absorption was observed, the 

 position for maximum resonance being about as well defined 

 as in the case of acetone. The D. C. 1 found is higher than the 

 D. C. of w^ater. This necessitated an extrapolation of the cali- 

 bration curve in order to get an approximate value. The D. 

 C. obtained in this way is 95.0 ± 3.5 After this exceedingly 

 high result had been obtained a second sample of hydrocyanic 



i The abbreviation D. C, is used for dielectric constant in the presentation of the re- 

 salts. 



