Formaldehyde. 
f  Am.  Jour.  Pbarm. 
\       April,  1898. 
I  to  4  c.c.  of  the  solution  to  be  tested,  according  to  the  presumed 
concentration.  It  forms  a  white  cloud,  which  is  finally  precipitated. 
After  forty-eight  hours  the  liquid  is  passed  through  filter  paper,  the 
precipitate  is  dried  at  400  C,  and  its  weight  determined.  The 
corresponding  quantity  of  formaldehyde  will  be  given  by  equation. 
C6H5NH2  -h  CH20  =  C6H5N  :  CH2  +  H20. 
The  method  employed  by  Dr.  Laderle,  Chief  Chemist  of  the  New 
York  City  Health  Department,  is  based  on  the  principle  that  am- 
monia and  formaldehyde  combine  readily  to  form  the  compound 
hexamethylentetramine,  according  to  the  following  reaction  : 
Formaldehyde.  Ammonia.  Hexamethylentetramine.  Water. 
6CH20       +       4NH3       =        (CH2)6N4         -f  6H20 
From  the  amount  of  ammonia  required  to  form  this  compound 
formaldehyde  is  calculated.  An  excess  of  ammonia  should  be  used 
and  the  mixture  allowed  to  stand  for  at  least  twelve  hours  ;  the 
excess  of  ammonia  present  is  determined  by  means  of  sulphuric 
acid. 
Method  of  Analysis. — Take  specific  gravity  of  the  solution  at 
room  temperature. 
Place  2  or  3  c.c,  carefully  measured,  into  a  bottle  with  glass  stop- 
N 
per;  add  50  to  60  c.c.    —  ammonia  solution;  shake  well  and  let 
N 
stand  twelve  hours,  shaking  occasionally.    Then  titrate  with  — 
sulphuric  acid,  using  coralline  as  indicator. 
Calculation — c.c.  of  ammonia  neutralized  by  formaldehyde  equal 
c.c.  of  ammonia  used,  minus  c.c.  of  sulphuric  acid. 
Then,  per  cent,  strength  of  solution  equal 
2-25  X  c.c.  ammonia  neutralized  by  formaldehyde 
Grammes  solution  taken. 
Uses  of  Formaldehyde. — Formaldehyde  has  been  put  to  an  almost 
endless  number  of  uses  in  the  arts  and  sciences,  but  it  is  its  great 
value  as  a  disinfectant  and  deodorizer  that  has  brought  it  into  such 
general  notice.  Early  in  its  history  it  was  noted  that  it  possessed 
strong  germicidal  and  preservative  powers,  and  many  forms  of  appa- 
ratus were  designed  in  the  attempt  to  render  it  available  for  the 
purposes  of  household  disinfection.    This  would  seem  to  be  a  very 
