464 
Note  on  Assay  of  Formaldehyde. 
(Am.  Jour.  Pharm 
(     October,  1911. 
lip  to  200  c.c.  From  this  point  the  procedure  was  the  same  as  that 
already  described.  Each  of  the  dif¥erent  conditions  of  time  and 
temperature  was  studied  with  three  different  KCN  excesses,  namely, 
a  KCN  excess  of  approximately  one-hundredth,  one-fourth,  and  one- 
half  of  an  equivalent,  respectively.  The  results  obtained  are  given 
in  Tables  II  and  III. 
Tab  LE^:  III 
Effect  of  Varying  the  Temperature 
No.  of 
experiment 
Amount  of 
formaldehyde 
solution 
taken 

Amount  of 
N/io  KCN 
added  c 
Amount  of 
N/io  AgNOs 
used 
N/io  KCNS 
required  for 
-J-  of  filtrate 
Found  equiva- 
lent of  the 
formaldehyde 
solution  in 
terms  of 
N/io  AgNOs 
•  Temperature:  5°C. 
(c.c.) 
(c.c.) 
(c.c.) 
(c.c.) 
(c.c.) 
I 
25 
33 
5 
I 
.90 
31 
50 
2 
25 
40 
1 2 
2 
•30 
32 
23 
3 
25 
48 
20 
2 
.38 
32 
32 
Temperature: 
I5°C. 
4 
25 
33 
15 
I 
.83 
31 
32 
5 
25 
40 
12 
2 
■30 
32 
18 
6 
25 
48 
20 
2 
.40 
32 
30 
Temperature: 
30°C. 
7 
25  ■ 
33 
5 
I 
.60 
30 
.86 
8 
25 
40 
1 2 
2 
.  20 
31 
.98 
9 
25 
48 
20 
2 
.40 
32 
•30 
Temperature: 
40°C. 
10 
25 
33 
5 
I 
•35 
30 
36 
II  I 
25 
40 
I  2 
2 
•15 
31 
88 
12 
25 
48 
20 
2 
•30 
32 
10 
C48  c.c.  of  the  KCN  solution  was  equivalent  to  47.56  c.c.  N/io  AgNOs  in  exps.  1-3;  to 
47.5  c.c.  N/  10  AgNOs  in  exps.  4-12. 
From  the  results  given  in  Table  II  it  is  seen  that  wdien  the  mixture 
of  KCN  and  formaldehyde  is  allowed  to  stand  42  hours  the  result 
obtained  is  practically  the  same  as  when  the  mixture  is  immediately 
added  to  the  silver  solution.  From  the  results  given  in  Table  III 
it  is  seen,  however,  that  a  variation  in  the  temperature  does  have  an 
appreciable  effect  on  the  results  obtained,  especially  when  the  KCN 
added  is  only  slightly  in  excess  of  that  required  to  combine  with  all 
of  the  formaldehyde  present.  That  this  is  so  may  also  be  seen  from 
the  following  experiments :  To  each  of  four  Erlenmeyer  flasks  there 
were  added  25  c.c.  of  a  dilute  formaldehyde  solution  and  33  c.c. 
