244     0XYGENNES1S,  FOR  THE  PRODUCTION  OF  OXYGEN,  ETC. 
binoxide  of  manganese  or  binoxide  of  lead  ;  the  cost  of  the  two 
first-mentioned  forbids  their  present  use,  and  the  one  selected 
is  by  far  preferable  to  the  others.  With  regard  to  the  acids, 
either  of  the  mineral  class  will  do,  but  I  prefer  a  mixture  of 
dilute  sulphuric  and  hydrochloric  acids. 
The  next  question  demanding  our  notice  is,  in  a  commercial 
point  of  view,  a  most  important  one ;  however  much  this  method 
may  be  admired  for  its  simplicity,  and  the  ease  with  which  the 
operation  may  be  conducted,  its  ultimate  success  or  failure  must 
depend  on  its  cost.  Can  the  oxygennesis,  therefore,  be  manu- 
factured and  sold  at  a  price  sufficiently  low  to  make  it  an  article 
of  commerce  ?  I  believe  it  can  be,  and  be  made  available  for 
all  purposes  wherever  oxygen  is  required  to  the  extent  of  some 
gallons.  One  of  the  ingredients  of  this  compound,  peroxide  of 
barium,  has  never  yet  been  produced  and  sold  as  a  commercial 
article,  and  from  the  trouble  of  making  a  small  quantity,  but 
few  even  practical  chemists  care  to  prepare  it  for  themselves. 
It  can  hardly,  therefore,  be  expected  that  a  compound  of  this 
nature  can  at  once  be  manufactured  and  sold  at  a  price  it  must 
ultimately  be  reduced  to,  if  extensively  used  and  produced  in 
quantity.  5s.  per  pound,  the  price  hitherto  charged,  would,  I 
admit,  be  a  barrier  to  its  general  adoption ;  but  I  am  happy  to 
say  we  have  now  made  the  necessary  arrangements  to  lessen 
the  cost  of  production,  and  have  at  the  same  time  reduced  the 
price. 
Some  of  the  baryta  compounds  are  found  abundantly  in  nature, 
and  are  of  but  small  value  in  the  market,  but  up  to  the  present 
time  but  few  uses  have  been  made  of  them ;  they  now  promise 
a  much  more  extensive  application.  Mr.  Kuhlman  has,  perhaps, 
done  more  than  any  one  else  to  develop  their  uses  and  value  in 
the  arts,  and  in  the  Chemical  News,  November  28,  1863,  will  be 
found  some  interesting  extracts  relating  to  them  from  Dr.  Hof- 
mann's  report  on  chemical  products  and  processes  of  the  Inter- 
national Exhibition. 
I  shall  trespass  a  little  further  on  your  time  to  make  a  few 
remarks  on  one  of  the  various  applications  of  oxygen,  which  may 
be  of  some  interest  to  the  medical  profession  and  to  pharmaceu- 
tical chemists.  I  mean  the  employment  of  that  body  as  a  the- 
rapeutic agent  by  inhalation.     For  that  purpose  this  ready 
