AmAJrff'  i9i8rm'  }    Disinfection  with  Formaldehyde.  295 
13.35  per  cent,  of  the  formalin,  would  be  oxidized  by  the  KMn04. 
With  the  proportions  recommended  by  Base  (100  Cc.  of  formalin 
to  50  Gm.  KMnOJ  7.12  Gm.  HCHO  or  17.8  per  cent,  of  the  formalin 
would  be  destroyed.  These  figures  are  considerably  lower  than 
those  found  in  the  investigations  mentioned  above.  In  any  event 
it  is  apparent  that  in  the  permanganate  process  a  considerable  part 
of  the  formaldehyde  used  as  formalin  is  destroyed  by  oxidation,  the 
reaction  supplying  the  heat  which  causes  the  rapid  volatilization  of 
the  remainder. 
It  may  be  assumed  that  the  behavior  of  the  chlorate  with  the 
formalin  is  entirely  analogous  to  that  of  the  permanganate,  and  that 
the  reaction  occurs  according  to  the  equation 
2KCIO3  +  3HCHO  =  2KCI  +  3H20  +  3C02. 
Experiments  have  shown  that  the  proportion  of  25  Gm.  of  chlorate 
to  100  Cc.  of  formalin  is  approximately  the  one  giving  best  results, 
that  is,  with  these  proportions  there  is  practically  no  liquid  left  in  the 
residue  after  the  reaction  subsides,  the  formaldehyde  being  either 
driven  off  as  gas  or  oxidized  and  the  water  evaporated  at  the  same 
time. 
A  simple  calculation  shows  that,  according  to  the  above  reaction, 
25  Gm.  KC103  will  theoretically  oxidize  9.18  Gm.  HCHO  or  nearly  23 
per  cent,  of  the  formaldehyde  in  the  100  Cc.  of  formalin,  leaving 
the  remaining  17  per  cent,  to  be  volatilized.  It  is  probable,  however, 
that  other  reactions  occur,  such  as 
KCIO3  +  3HCHO  =  KC1  +  3HCOOH. 
In  fact,  appreciable  amounts  of  formic  acid,  as  well  as  C02,  are 
evolved  by  the  reaction  of  formalin  with  either  permanganate  or 
chlorate. 
In  an  attempt  to  determine  in  a  simple  manner  the  best  propor- 
tions of  formalin  and  chlorate,  a  series  of  roughly  quantitative  ex- 
periments were  made,  using  varying  proportions  of  the  two  ma- 
terials. A  weighed  amount  of  powdered  KC103  was  treated  in  a 
beaker  with  a  weighed  amount  of  the  40  per  cent,  formalin  and  the 
beaker  immersed  in  hot  water  in  order  to  start  the  reaction.  The 
residue  left  in  the  beaker  after  the  reaction  had  ceased  was  dis- 
solved in  water  and  titrated  with  standard  solution  of  silver  nitrate 
to  determine  the  amount  of  chloride  present.  From  the  amount  of 
KC1  found,  the  weight  of  formalin  representing  the  formaldehyde 
