436 
Obituaries. 
f  Am.  Jour.  Pharrn . 
I  September,  1907. 
lishing  important  papers,  chiefly  on  physics.  In  1863  he  returned 
to  St.  Petersburg,  where  he  remained  for  the  rest  of  his  life.  He 
began  shortly  after  the  publication  of  his  "  Principles  of  Chemistry," 
of  which  seven  editions  have  appeared  in  Russian  and  three  in 
English.  While  engaged  upon  this  work,  he  announced  his  views 
of  the  arrangement  of  the  elements  according  to  the  Periodic  Law 
in  1869.  While  similar  views  had  been  advanced  before  in  vague 
outlines,  Mendelejeff's  theory  showed  how  all  the  physical  and 
chemical  properties  of  the  elements  could  be  deduced  from  their 
position  when  arranged  according  to  the  order  of  their  atomic 
weights.  He  went  further  and  showed  where  hypothetical  and  as 
yet  undiscovered  elements  should  find  their  place  in  his  arrangement 
and  predicted  their  physical  and  chemical  properties  with  many 
details.  The  discovery  of  gallium  (1875),  germanium  (1886)  and 
scandium  (1888),  and  the  exact  correspondence  of  these  elements  in 
all  respects  with  three  of  the  hypothetical  elements  predicted  by 
Mendelejeff,  confirmed  in  the  minds  of  chemists  the  value  of  his  theory 
and  the  fitting  into  his  system  of  the  five  rare  atmospheric  gases 
by  Ramsey  again  demonstrated  its  great  importance  as  a  working 
theory.  Mendelejeff,  however,  devoted  much  of  his  time  to  impor- 
tant practical  and  economic  problems.  He  visited  America  in  1876 
at  the  instance  of  the  Russian  Government  to  study  the  Pennsyl- 
vania oil  production,  and  on  his  return  devoted  his  efforts  to  the 
scientific  development  of  the  Russian  oil  industry.  At  the  same 
time  he  put  forward  a  new  theory  of  the  origin  of  petroleum  which 
has  found  many  advocates.  He  also  acted  as  the  adviser  of  his 
Government  in  many  other  directions,  studying,  for  example,  nitro- 
explosives  and  inventing  a  smokeless  powder  for  them.  He  retained 
his  mental  and  physical  powers  unimpaired  until  shortly  before  his 
death  at  the  age  of  seventy-three. 
A  week  or  two  after  the  announcement  of  the  death  of  Mende- 
lejeff, in  February  of  this  year,  came  the  announcement  of  the  death, 
following  an  operation  for  appendicitis,  of  the  eminent  French 
chemist,  Moissan.  Unlike  the  two  just  mentioned,  Moissan  was  in 
the  prime  of  life,  not  having  reached  his  fifty-fifth  year  of  age. 
Unlike  the  others,  also,  Henri  Moissan  has  been  officially  connected 
with  pharmacy  during  most  of  his  active  career,  having  secured,  in 
1879,  the  appointment  of  "  Chief  of  Practical  Exercises,"  equivalent 
to  a  demonstratorship,  in  the  "  Ecole  Superieure  de  Pharmacie,"  of 
