9o  Testing  of  Formaldehyde.  {^^Xt' 
for  assay,  the  work  was  restricted  to  the  use  of  the  stronger  solution. 
Only  one  trial  with  a  decinormal  solution  was  made,  which  indi- 
cated that  the  assay  would  require  about  one  hour,  and  that  rosolic 
acid  is  not  sufficiently  sensitive  in  presence  of  hexamethylene-tetra- 
mine  to  give  serviceable  results  until  after  some  practice. 
Experiments  with       ammonia  solution  :  25  c.c.  of  the  ammonia 
solution  were  run  from  a  burette  into  a  flask  and  2  25  grammes 
of  sample  added.  The  flask  was  then  closed  with  a  glass  stopper 
thickly  coated  with  vaseline.    The  mixtures  were  allowed  to  stand 
ft 
a  definite  time,  and  then  the  excess  of  ammonia  titrated  with  _  sul- 
1 
n 
phuric  acid,  using  rosolic  acid  as  indicator.  Each  c.c.  of  —  ammo- 
nia corresponds  to  0-045  gramme,  or  0-5  per  cent.,  when  2-25 
grammes  are  taken. 
Per  cent. 
Titrated  at  once  after  admixture  36*0 
"       after  15  minutes    .  .  .  374 
"         "     1  hour  37-5 
"     2  hours  37 -5 
"     standing  over  night   .  37*4 
Other  trials,  previously  made  in  flasks  closed  with  rather  loosely- 
fitting  rubber  stoppers,  gave  somewhat  variable  figures,  the  ten- 
dency being  too  high  results  through  loss  of  ammonia,  particularly 
when  considerable  time  elapsed  before  titrating. 
Assay  in  Presence  of  Acetone. — A  mixture  of  2-25  grammes  of  for- 
n 
maldehyde  solution,  25  c.c.  of  -  ammonia,  and  0-5  c.c.  of  pure  ace 
tone  was  allowed  to  stand  20  minutes  and  then  titrated.  The  solu- 
tion was  assayed  in  a  similar  manner  without  addition  of  acetone. 
Per  Cent. 
Without  acetone  34'9>  347 
With  "   34"8,  35'o 
Assay  in  Presence  of  Methyl  Alcohol. — A  mixture  of  2-25 
grammes  of  formaldehyde  solution  (not  the  solution  used  in  the 
preceding  experiments),  0-5  c.c  of  methyl  alcohol,  pure  or  commer- 
cial,  and  25  c.c.  of  -  ammonia,  was  treated  in  the  same  manner  as 
above,  and  the  formaldehyde  solution  also  assayed  without  addition. 
