Am.  Jour.  Pharm. ) 
October,  1911.  J 
Note  on  Assay  of  Formaldehyde. 
463 
stoppers  and  the  value  of  the  KCN  solution  was  controlled  by 
letting-  it  stand  under  similar  conditions  and  determining  its  strength 
at  the  end  of  the  experiment.  The  experiments  designed  to  show 
the  effect  of  temperature  were  carried  out  as  follov/s :  The  formalde- 
hyde solution  was  placed  in  one  Erlenmeyer  flask  while  the  KCN 
solution  which  was  to  be  added  to  it  was  placed  in  another  similar 
flask  and  both  were  then  warmed  or  cooled  to  the  desired  tempera- 
ture by  being  set  in  a  large  water-bath  which  was  kept  about  a  degree 
above  or  below  the  desired  temperature,  respectively.  The  time  thus 
consumed  was  about  half  an  hour.  The  KCN  solution  was  then 
poured  intO'  the  flask  containing  the  formaldehyde  solution  and 
the  mixture  quickly  transferred  .back  again  into  the  flask  which 
contained  the  KCN  solution  and  mixed  in  the  usual  way  while  the 
flask  containing  the  solutions  was  still  immersed  in  the  water-bath. 
This  mixture  was  then  quickly  poured  into  a  mixture  of  silver 
nitrate  and  nitric  acid,  in  a  200  c.c.  measuring  flask,  and  mixed 
with  it.  Both  flasks  were  then  thoroughly  washed  with  distilled 
water,  the  washinp-s  added  to  the  silver  solutioii,  and  the  whole  made 
No.  of 
experi- 
ment 
I 
2 
3 
4 
5 
6 
7 
8 
9 
10 
II 
12' 
Table  II. 
Effect  of  Varying  the  Time. 
Temperature  :   15°  c. 
Amount  of     Amount  of 
Time  mix- 
ture stood  Amount  of 
before  formalde-    ^wr^  ^^'m\^    ^t/t^  irvMo  icnianci 
added  to  hydesolu-    ""iZS?^    "^^'^il^^^     for  ^  of 
silver  tion  taken  '^^ciea 
used 
Found  equivalent 
n/io  KCNS    of  the  formal- 
required       dehyde  solu- 
tion in  terms 
of  n/io 
solution 
Hours 
18 
18 
18 
42 
42 
42 
(c.c.) 
25 
25 
25 
25 
25 
25 
25 
25 
25 
25 
25 
25 
(c.c.) 
33 
40 
48 
33 
40 
48 
33 
40 
48 
33 
40 
48 
(c.c.) 
5 
12 
20 
5 
12 
20 
5 
12 
20 
5 
12 
20 
filtrate 
(  c.c.  ) 
1.80 
2.30 
2.38 
1.80 
2.30 
2.40 
1.82 
2.25 
2.35 
1.85 
2.30 
2.35 
*  Added  immediately  after  mixing. 
b  48  c.  c.  of  the  KCN  sol.  was  found  equivalent  to  47-6  c.  c.  n/io  AgNOs, 
AgNO,3 
(c.c.) 
31-33 
32.27 
3236 
3 1-33 
32.27 
32.40 
31-  37 
32-  17 
32.30 
31-43 
32.27 
32.30 
"*Thc  amount  of  A^^NO:,  varied  as  shown  in  the  tables,  while  the  amount 
of  HNO.-i  was  the  same  in  all  eases,  namely,  20  c.c.  of  jo  ])er  cent,  nitric  acid. 
