of  Dielectric  Constants  of  Non-conducting  Liquids.        79 
It  will  be  seen  from  the  above  that  the  results  are  approxi- 
mately within  an  error  of  1  per  cent. 
The  dielectric  constants  of  certain  organic  liquids  were 
determined  to  test  the  accuracy  o£  the  method. 
Benzene. 
The  sample  (thiophene  free)  was  purchased  of  Kahlbaum, 
and  subsequently  purified  by  freezing  and  distilling  over 
sodium  ;  the  following  results  were  obtained  : — 
Temperature  17°. 
L  (Air). 
R 
(Air)  condenser  fixed  at 
7*680  mms. 
7*615  mms. 
L  (readings). 
Benzene  introduced. 
3-3 
34 
3-4 
3-42 
3'4 
dean     3*384 
7*68 
Dielectric  constant  K=  =  2*27. 
Nernst*  gives  2*258  for  carefully  dried  benzene,  Thwingf 
2*310  as  a  mean  of  nine  observers  ;  the  value  given  above  is 
approximately  the  mean  of  these  two  values. 
Another  set  of  observations,  probably  less  accurate,  was 
made  in  the  reverse  manner,  namely,  by  varying  the  benzene 
condenser  and  keeping  the  air-condenser  constant  ;  the  mean 
value  of  nine  concordant  observations  gave  K  =  2*267,  which 
differs  from  the  above  approximately  in  the  ratio  1/600. 
Carbon  Tetrachloride. 
Purchased  of  Kahlbaum,  purified  by  fractional  distillation, 
the  portion  coming  over  between  76°*59  and  76°*99  being  col- 
lected. Mean  boiling-point  760,79  at  Bar.  750*4  (corr.). 
Density  4/4  =  1*62611  (corr.  to  vacuum).  Thorpe {  gives 
the  values  for  B.P.  =  76°*76  at  755*4,  and  D.  0/4=1*63195. 
Young  §  for  B.F.  =  76°*75  at  750*1.  These  several  values  are 
concordant. 
*  Loc.  cit.  supra,  p.  658. 
t  Zeits.  f.physikal.  Chem.  xiv.  p.  300  (1894). 
t  Phil.  Trans.  1894  (A),  p.  494,  and  Joura.  Chem.  Soc.  1880,  Trans, 
p.  59. 
§  Journ.  Chem.  Soc.  1891,  Trans,  p.  91*2. 
