294  Disinfection  with  Formaldehyde.    {AEIA^yr-  Ig^|rm' 
float,,  placed  in  a  large  shallow  pan  (an  ordinary  dish  pan  will 
answer  the  purpose)  containing  water  heated  to  about  the  boiling 
point. 
The  mixture  becomes  heated  to  the  reaction  temperature  in  a 
few  minutes,  when  bubbles  of  gas  begin  to  be  evolved,  this  evolu- 
tion increasing  rapidly  until  it  is  so  violent  that  the  mixture  may 
foam  over  the  top  of  the  bucket.  The  action  is  completed  in  2  or  3 
min.,  and  with  the  proper  proportion  of  chlorate  and  formalin  the 
residue  remaining  in  the  bucket  is  practically  dry  and  consists  chiefly 
of  chloride  together  with  some  unreduced  chlorate. 
Sodium  chlorate  seems  to  give  just  as  satisfactory  results  as  po- 
tassium chlorate,  and  has  the  distinct  advantage  of  costing  less 
than  one  half  as  much  as  the  latter.  Potassium  chlorate  is  now 
quoted  at  50  to  55  cents  per  lb.,  while  sodium  chlorate  is  listed  at 
24  to  25  cents. 
Several  investigators  have  attempted  to  determine  what  propor- 
tion of  formaldehyde  used  in  the  permanganate  process  is  liberated 
as  gas  and  what  proportion  is  oxidized  by  the  reaction.  Frank- 
forter  and  West4  obtained  an  evolution  of  62  per  cent,  to  75  per 
cent,  of  the  formaldehyde  from  formalin  by  this  process  in  a  long 
series  of  experiments  under  laboratory  conditions,  using  glass  ap- 
paratus and  absorbing  the  evolved  gas  in  water,  the  strength  of  the 
resulting  solution  being  determined.  D.  Base,5  in  experiments  with 
the  process  on  a  practical  scale,  used  a  specially  prepared  room  of 
2,000  cu.  ft.  capacity,  determining  the  amount  of  formaldehyde 
gas  in  the  room  by  drawing  5-  to  10-liter  samples  through  standard 
KCX  solution,  adding  excess  of  standard  AgNOs  solution  and  ti- 
trating the  excess  of  the  latter  with  sulphocyanate.  Base  found  that 
not  over  40  per  cent,  of  the  total  amount  of  formaldehyde  used  as 
formalin  was  evolved  in  the  state  of  gas  in  the  room. 
It  has  been  suggested  that  the  reaction  between  formaldehyde 
and  potassium  permanganate  is  probably  as  follows : 
4KMn04  +  3HCHO  +  H20  =  4Mn(OH)2  +  2KXO3  +  C02. 
It  is,  however,  likely  that  other  reactions  proceed  at  the  same  time, 
in  which  part  of  the  formaldehyde  is  oxidized  to  formic  acid.  As- 
suming this  reaction,  however,  it  is  calculated  that  with  the  propor- 
tions recommended  by  Evans  and  Russell  (100  Cc.  of  40  per  cent, 
formalin  to  37.5  Gm.  KMn04)  5.34  Gm.  of  formaldehyde,  or  about 
4 /.  Am.  Chem.  Soc,  28  (1906),  1234. 
5  Ibid.,  28  (1906),  964. 
