Amju°nei;,i9oh2frm"}     Manufacture  of  Sulphuric  Acid.  285 
Schmiedeberg  states  (Arzneimittellehre,  p.  190)  that  one  may  take 
it  with  enough  certainty  that  all  indigestible  colloidal  substances,  to 
wit,  gums  and  mucilage  of  plants,  not  only  themselves  remain 
longer  in  the  stomach  and  intestine,  but  also  delay  the  absorption  of 
other  substances,  and  E.  Leibert  (reported  by  H.  v.  Tappeiner, 
Archives  Internationales  de  Pharmacodynamic  et  de  Th'erapie,  Vol.  10, 
p.  85,  1902)  showed  that  colloids  markedly  hinder  the  effects  of 
dilute  solution  of  chloral  hydrate,  and  Rott  {ibid.,  p.  93)  showed  that 
this  difference  existed  also,  with  or  without  gums,  when  the  solution 
of  chloral  hydrate  was  introduced  into  the  intestines. 
Cleveland,  O.,  May  7,  1902. 
THE  NEW  CONTACT  METHOD  FOR  THE  MANUFAC- 
TURE OF  SULPHURIC  ACID. 
By  Prof.  Samuel  P.  Sadt^kr. 
The  importance  of  sulphuric  acid  as  the  foundation  of  most 
chemical  industries  is  generally  impressed  upon  every  chemical 
student.  His  attention  is  called  to  the  fact  that  all  the  other 
mineral  acids  are  obtained  by  its  aid  from  the  minerals  or  salts  in 
which  they  are  bound  up  in  nature  and  that  many  of  the  elements 
are  also  obtained  by  reactions  in  which  its  use  is  found  to  be  indis- 
pensable. It  is  to  be  remembered,  too,  that  some  of  the  most 
important  organic  products  are  only  obtainable  by  the  aid  of  the 
concentrated  or  fuming  sulphuric  acid,  as  alizarine  and  artificial 
indigo.  The  question  of  its  manufacture  on  a  large  scale  cheaply 
becomes  therefore  of  the  first  importance. 
The  chemical  reaction  underlying  its  production  is  an  extraordi- 
narily simple  one.  It  merely  involves  the  union  of  sulphur  dioxide 
with  an  atom  of  oxygen  to  form  sulphur  trioxide,  and  this  takes  up 
moisture  with  avidity  to  form  the  molecule  of  sulphuric  acid.  While 
this  reaction  of  sulphur  dioxide  and  oxygen  is  an  exothermic  one, 
it  takes  place  very  slowly,  unless  aided  by  some  catalytic-acting 
material.  In  the  well-known  lead-chamber  process,  this  material 
acting  as  the  carrier  of  oxygen  is  a  mixture  of  the  oxides  of  nitrogen, 
obtained  by  the  decomposition  of  nitric  acid  or  a  nitrate.  This 
process,  after  having  served  for  over  a  century  as  the  only  one 
capable  of  being  used  on  a  manufacturing  scale,  is  likely  to  be 
replaced  in  the  near  future  by  what  seems  to  be  a  simpler  one, 
