A  m.  Jour.  Pharm.  ) 
January,  1920.  ) 
Report  on  Atomic  Weights. 
35 
the  last  value,  rounded  to  162.5,  seems  to  be  the  one  best  entitled 
to  acceptance. 
Erbium. — For  this  element,  by  the  oxide-chloride  method, 
Wichers,  Hopkins  and  Balke^^  obtained  values  ranging  from  Er  = 
168.00  to  168.84.  The  method  of  determination  is  thus  again 
shown  to  be  untrustworthy. 
Thorium. — In  a  long  series  of  concordant  analyses  of  thorium 
bromide,  Honigschmid^^  finds  Th  =  232.152  from  the  silver  ratio 
and  232.150  from  the  silver  bromide  ratio  when  Br  =  79.916.  The 
value  Th  =  232.15  should  be  adopted  for  general  use.  He  also 
studied  thoria  from  uranium  ores,  which  contained  ionium.  For 
this  mixture  he  obtained  an  atomic  weight  slightly  in  excess  of  231.50. 
This  may  approximate  to  the  unknown  atomic  weight  of  ionium. 
Uranium. — The  later  series  of  determinations  of  the  atomic 
weight  of  uranium  by  Honigschmid  and  Horovitz^^  was  based  like 
their  earlier  series  upon  analyses  of  the  tetrabromide.  Two  sets  of 
analyses  were  made,  one  upon  a  bromide  which  had  been  fused  in 
bromine  vapor,  the  other  in  nitrogen.  The  value  obtained  ranged 
from  U  =  238.04  to  238.16,  the  latter  being  in  harmony  with  their 
former  determinations.  The  rounded  figure  238.2  is  given  in  the 
table. 
HE1.IUM. — Taylor,  28  using  the  microbalance  for  determining  the 
density  of  helium,  finds  He  =  4.0008.  Guye,^^  in  a  recalculation 
of  the  data,  finds  He  =  3-998.    The  value  4  should  be  retained. 
Argon. — From  the  density  and  compressibility  of  argon,  Leduc^^ 
finds  A  =  39.91.  He  regards  the  second  decimal  as  uncertain,  and 
advises  the  adoption  of  the  rounded  value  39.9. 
In  the  following  table  of  atomic  weights  proposed  for  1920,  few 
changes  have  been  made  from  the  values  given  in  the  U  st  preceding 
table.  The  new  values  are  A  =  39.9;  B  =  10.9;  Ga  =  70.1;  Th  = 
232.15;  and  Yt  =  89.33.  addition  to  these  the  atomic  weight  of 
nitrogen  should  be  changed  from  14.01  to  the  more  precise  value 
14.008.    The  latter  figure  represents  all  the  best  determinations^ 
26  /.  Amer.  Chem.  Soc,  40:  1615,  1918. 
2s  Z.  Electrochem.,  22:  18,  1916. 
2  Monatsh.,  37:  185,  1916. 
28  Phys.  Rev.,  10:  653,  1917. 
23  /.  chim.  phys.,  16:  46,  1918. 
»°  Compt.  rend.,  167:  70,  1918. 
