333  Abstracts  from  the  French  Journals.  {^jS&StT*' 
do  not  change  in  appearance  and  preserve  the  active  principle  inde- 
finitely :  Triturate,  kaolin  2  ;  anhydrous  sodium  sulphate,  I  ;  and 
water,  I  ;  the  mass  remains  plastic  during  6-IO  minutes,  but  after 
fifteen  minutes  becomes  so  hardened  that  it  can  be  thrown  on  the 
floor  without  danger  of  breaking.  With  this  mass  the  medicament 
in  fine  powder  is  incorporated. 
Detection  of  hydrocyanic  acid. — Dr.  Soura  Lopez  [Rev.  dos  curs, 
de  med.  do  Rio  de  Janeiro,  through  Jour,  de  pharm.  et  de  chim. 
June,  1893,  P-  55°)  publishes  the  following  process,  based  upon  the 
reaction  of  mercuric  cyanide  with  solution  of  ammonium  chloride. 
Milk  of  lime  in  excess  is  added  to  the  suspected  material  and  heated 
to  ioo°  C.  on  the  water-bath.  The  lime  decomposes  the  ammonia- 
cal  salts,  disengaging  all  the  ammonia  ;  after  the  cessation  of  the 
alkaline  fumes,  the  hot  solution  is  filtered  and  introduced  into  a 
retort  with  an  excess  of  pure  bicarbonate  of  sodium  ;  heated  to  6o° 
the  sodium  salt  decomposes  the  alkali  cyanides,  liberating  hydro- 
cyanic] acid,  but  does  not  attack  potassium  ferrocyanide,  which  is 
decomposed  by  carbonic  acid  slowly  after  several  hours,  with  the 
gradual  evolution  of  hydrocyanic  acid.  If  the  mercuric  cyanide  is 
combined  with  potassium  ferrocyanide,  sodium  sulphide  is  placed  in 
the  retort,  this  acting  upon  the  mercuric  cyanide  by  double  decom- 
position, in  producing  mercuric  sulphide  and  sodium  cyanide;  then 
sodium  bicarbonate  will  liberate  hydrocyanic  acid,  acting  upon  the 
sodium  cyanide.  If  the  distilled  product  is  added  to  silver  nitrate 
solution,  containing  hydrocyanic  acid  in  the  form  of  silver  cyanide, 
traces  of  the  acid  will  remain  unnoticed,  since  the  silver  nitrate 
solution  dissolves  a  little  of  the  cyanide ;  the  author  therefore  uses 
ammoniacal  silver  nitrate,  taking  care,  however,  not  to  have 
the  ammonia  in  excess.  For  determining  the  cyanide  as  Prussian 
blue,  dissolve  the  silver  cyanide  in  solution  of  sodium  hyposulphite, 
add  ferrous  sulphate  and  then  an  excess  of  potassa ;  agitate  the 
solution  without  excluding  the  air  and  add  a  slight  excess  of  hydro- 
chloric acid.  The  Prussian  blue  must  be  separated  at  once  by  filtra- 
tion, to  prevent  the  formation  of  silver  sulphate,  and  to  obtain  a  sensi- 
tive end  reaction. 
Estimation  of  caffeine. — Alex.  Grandval  and  Henri  Lajoux  publish 
the  following  process  in  Jour,  de  pharm.  et  de  chim.,  June,  1893,  pp. 
545  to  549  : 
The  substance  to  be  examined  is  finely  pulverized,  5  gm.  of  it 
