502  Formaldehyde  in  Witch  Hazel.  {November 'SSm 
reagent  by  rotation  and  the  color  observed  after  five  minutes.  In  no  case  was  a 
red  coloration  observed.  When  a  i  per  cent,  formaldehyde  solution  was  tested 
a  decided  red  color  developed. 
(2)  The  reagent  was  prepared  by  dissolving  o-i  gramme  salicylic  acid  in 
100  c.c.  sulphuric  acid.  The  formaldehyde  dilutions  were  tested  as  in  1,  with 
these  results  : 
(a)  1  in  1,000  water.    Deep  red  color. 
(3)  1  in  1,000  15  per  cent,  alcohol.    Deep  red  color. 
(c)  1  in  10,000  water.    Rose  color,  much  lighter  than  a. 
(d)  1  in  10,000  15  per  cent,  alcohol.    Distinct  rose  color,  much  less  than  c. 
(e)  and  (f)  No  red  coloration. 
(3)  The  reagent  was  prepared  by  dissolving  o-oi  gramme  salicylic  acid  in 
100  c.c.  sulphuric  acid.    The  formaldehyde  dilution  tested  as  in  1  showed  : 
(a)  1  in  1,000  water.    Color  was  deep  red,  somewhat  less  intense  than  2  a. 
(b)  1  in  1,000  15  per  cent,  alcohol.    Color  deep  red,  less  intense  than  3  a. 
(c)  1  in  10,000  water.    Color  rose  red,  deeper  than  2  c  and  nearly  equal 
to  3  b. 
(d)  1  in  10,000  15  per  cent,  alcohol.    Color  more  pronounced  than  2  c. 
(e)  and  {/)  No  red  coloration. 
(4)  When  the  reagent  was  prepared  by  dissolving  o-ooi  gramme  salicylic 
acid  in  100  cc.  sulphuric  acid,  very  faint  traces  of  reddish  color  developed  with 
solutions  a  and  c  only. 
(5)  The  reagent  was  prepared  by  dissolving  o'oi  gramme  salicylic  acid  in 
100  c.c.  of  a  weaker  sulphuric  acid,  having  a  specific  gravity  of  1  8090  at  25/25 
degrees.    Tested  as  before,  after  five  minutes  the  colors  were  : 
(a)  1  in  1,000  water.    Red  color  distinct,  but  much  less  intense  than  3  a. 
(b)  1  in  1,000  15  per  cent,  alcohol    Red  color,  less  intense  than  3  a. 
(c)  1  in  10,000  water.    Red  color,  less  intense  than  5  b. 
(d)  1  in  10,000  15  per  cent,  alcohol.    Red  tinge  hardly  perceptible. 
At  the  end  of  an  hour  these  colors  all  became  more  intense  and  after  several 
hours  closely  approached  those  obtained  in  3. 
(6)  To  portions  of  5  c.c.  of  the  reagent,  prepared  as  at  3,  was  added  o-6  c.c, 
o*8  c.c,  1  c.c,  1*2  c.c,  1 '4  c.c,  i*6  cc,  i'8  cc,  2  c.c.  of  the  dilution  c,  con- 
taining 1  of  formaldehyde  in  10,000  water.  The  intensity  of  the  color  increased 
with  the  added  quantity  of  formaldehyde  dilution  up  to  1*4  cc  and  then  re- 
mained constant. 
The  dilution  d,  containing  1  in  10,000  15  per  cent,  alcohol,  when  used  in  the 
same  way  gave  similar  results.  When  o*6  c.c  was  used  the  red  was  barely  per- 
ceptible ;  the  intensity  then  increased  until  i'4  c.c  were  added,  and  then  again 
remained  the  same  when  still  larger  volumes  of  the  formaldehyde  dilution  were 
used. 
(7)  The  reagent  prepared  as  at  3  and  allowed  to  stand  over  night,  eighteen 
hours,  was  found  to  be  inert,  i.  e.,  did  not  show  the  presence  of  formaldehyde 
in  any  of  the  dilutions  used  above. 
These  experiments  show  that  the  official  formaldehyde  test,  when 
properly  applied,  will  show  the  presence  of  I  gm.  ot  formaldehyde 
in  10,000  c.c.  of  a  15  percent,  alcohol. 
