Am.  Jour.  Pharm.  I 
November,  1913.  J 
The  Phenomena  of  Catalysis. 
509 
diminished.  In  such  cases  it  seems  necessary  to  grant  that  the  time 
necessary  for  the  catalyst  to  unite  with  one  of  the  reagents,  and 
for  the  second  to  enter  the  reaction  and  the  catalyst  to  back  out, 
so  to  speak,  is  in  all  shorter  than  the  time  necessary  for  direct 
union  of  the  reacting  substances.  This  is  possible.  The  catalyst 
often  seems  to  be  merely  a  means  of  in  some  way  reducing  the 
delays  in  a  process.  It  can  hardly  be  said  to  reduce  the  resistance 
to  reaction,  for  reduction  of  resistance  should  cause  a  change  in  the 
total  heat  evolved  by  the  reaction,  and  this  does  not  occur. 
Any  treatment  of  this  subject  would  be  incomplete  which  did 
not  mention  the  phenomenon  of  anti-catalysis  or  negative  catalysis. 
As  the  name  implies,  this  is  the  case  where  the  presence  of  some 
otherwise  inactive  substance  retards  or  prevents  a  reaction  which 
would  otherwise  take  place.  In  biological  chemistry  there  are 
many  such  cases,  and  they  are  frequently  referred  to  as  poisonings. 
One  of  the  best  known  inorganic  cases  is  that  described  by  Bredig, 
who  found  that  while  the  decomposition  of  hydrogen  peroxide 
was  catalyzed  by  colloidal  platinum',  iridium,  etc.,  the  presence  of 
almost  any  one  of  the  common  soluble  poisons  was  capable  of  de- 
stroying the  action  of  the  catalyst  and  of  preventing  the  reaction. 
Hydrocyanic  acid,  hydrogen  sulphide,  arsenic,  copper  salts,  etc., 
are  such  poisons.  These  poisons  also  act  as  anti-catalyzers  to  a 
number  of  biochemical  reactions,  ferment  actions,  etc.  Water  in 
most  cases  is  an  active  catalyzer,  but  a  few  cases  have  been  found 
where  it  is  distinctly  an  anti-catalyst.  Oxalic  acid,  dissolved  in 
dry  sulphuric  acid,  decomposes  very  rapidly,  but  the  presence  of 
traces  of  water  greatly  diminishes  the  velocity.  The  hydro- 
gen ion  is  a  generally  active  catalyzer.  It  shows  its  power  in 
many  cases  of  hydrolysis  and  in  the  action  of  enzymes,  etc.  The 
hydrolysis  of  cane  sugar  by  acids  depends  upon  it. 
A  multitude  of  reactions  for  which  solid  catalyzers  have  been 
found  may  be  represented  by  one  or  two  specific  cases.  Ammonia 
and  alcohol  vapors  combine  rapidly  in  the  presence  of  heated 
thorium  oxide,  so  also  do  phenols  and  alcohols.  Titanium  oxide 
and  other  metal  oxides  catalyze  organic  reactions  without  there 
appearing  to  be  any  predeterminable  predilection.  One  is  led  to 
imagine  that  every  possible  chemical  reaction  has  its  specific  cata- 
lyzers. Haber  has  said  that  every  solid  substance  exerts  some 
accelerating  action  on  gaseous  reactions,  though  some  do  it  much 
more  markedly  than  others. 
