86  Gleanings  from  the  German  Journals.  {Am*E^Y$Ta* 
of  furfurol  in  a  liter  of  the  glacial  acetic  acid. — Ber.  d.  Deutch.  Chem* 
Ges.,  1878,  p.  1870. 
Phenolphthalein1  Indifferent  to  Bicarbonates. — Experiments  with 
phenolphthalein,  the  use  of  which  is  recommended  when  saturating 
alkaline  carbonates  with  acid,  convinced  Vielhaber  that  alkaline  bicar- 
bonates have  not  the  least  effect  upon  it. — Arch.  d.  Pharm.,  Nov., 
1878,  p.  410. 
Delicacy  of  Several  Tests  for  Hydrocyanic  Acid. — A.  Link  and 
R.  Moeckel  made  a  series  of  experiments  in  order  to  investigate  the 
delicacy  of  different  tests  for  hydrocyanic  acid  with  the  following 
results  : 
l.  The  silver  test  (precipitation  of  cyanide  of  silver). — On  the  addi^ 
tion  of  a  solution  of  silver  to  an  acidulated  concentrated  solution  of 
hydrocyanic  acid,  a  precipitate  is  immediately  formed;  but  if  the  liquid 
is  much  diluted  it  is  necessary  to  add  an  excess  of  ammonia  before  the 
silver  solution  is  added,  and  to  acidulate  afterwards  with  nitric  acid- 
No  reaction  takes  place  if  the  hydrocyanic  acid  is  diluted  in  the  pro- 
portion of  1  : 250,000. 
2.  Ferrocyanide  of  Iron  Test. — The  precipitation  of  ferrocyanide  of  iron 
in  a  solution  of  hydrocyanic  acid,  to  which  one  drop  of  a  moderately 
concentrated  solution  of  sulphate  of  iron  containing  ferric  salt,  and 
sufficient  diluted  solution  of  potassa  to  yield  an  alkaline  reaction,  had' 
been  added,  begins  to  be  doubtful  in  a  dilution  of  1  :50,00c 
3.  Sulphocyanate  of  Iron  Test. — This  is  the  most  delicate  test.  After 
the  addition  of  1  drop  of  a  dilute  solution  of  soda-lye  to  the  hydros- 
cyanic  acid  solution,  sulphydrate  of  ammonium  is  added,  the  mixture 
evaporated  to  dryness,  and  to  the  residue  a  few  drops  of  hydrochloric 
acid  and  of  ferric  chloride  are  added.  The  resulting  blood-red  color  can 
be  noticed  in  a  dilution  of  1  14,000,000,  although  it  has  then  an  orange 
tint. 
4.  Guai  a  cum- Copper  Test. — Strips  of  white  filtering-paper  are  dipped 
into  a  4  per  cent,  solution  of  resin  of  guaiacum  and  moistened  with  & 
drop  of  a  \  per  cent,  solution  of  sulphate  of  copper.  The  character- 
istic blue  reaction  resulting  when  brought  into  contact  with  the  hydro- 
cyanic acid  solution  takes  place,  when  diluted  in  the  proportion  of 
1  : 3,000,000. 
1  See  paper  by  C.  W.  Drew  in  "Amer.  Jour.  Pharm.,"  1878,  p.  513. 
