396  Practical  Notes  from  Various  Sources.  {Av^iguli,m7Tm' 
PKACTICAL  NOTES  FROM  VARIOUS  SOURCES. 
By  the  Editor. 
Permanent  solution  of  mercuric  chloride. — On  dissolving  mercuric 
chloride  in  other  than  distilled  water,  a  precipitate  of  oxychloride  is 
usually  produced  by  the  earth  carbonates  in  the  water.  Prof.  O. 
Angerer  ( Centralbl.  f.  Chir.,  1887,  p.  7),  states  that  Schilling  succeeded 
in  preventing  this  precipitate  by  the  addition  of  sodium  chloride  equal 
in  quantity  to  that  of  the  corrosive  sublimate.  Schilling  prepares 
also  corrosive  sublimate  tablets  from  1  gm.,  or  0.5  gm.  each  of  the  two 
salts  mentioned ;  these  tablets  dissolve  rapidly,  and  are  adapted  for 
distilled  or  any  Other  pure  water. 
The  facts  upon  which  the  above  is  based,  were  ascertained  in  1857 
by  Voit  (Ann.  Chem.  Phar.,  civ.  341)  in  researches  made  for  an 
entirely  different  purpose.  He  proved  the  existence  of  two  double 
salts  NaCl.  HgCl2  and  2  IS"aCl.HgCl2,  both  of  which  are  freely  soluble 
in  water,  and  these  solutions  if  not  too  dilute,  may  be  rendered  dis- 
tinctly alkaline  by  caustic  soda  without  being  precipitated ;  excess  of 
soda  causes  the  appearance  of  a  white,  then  red-brown,  etc.,  precipitate, 
but  this  appears  later,  and  is  less  rich  in  mercuric  oxide,  if  a  sufficient 
excess  of  sodium  chloride  is  present. 
Almen's  test  for  sugar  is  a  modification  of  Bottger's  test,  the  reagent 
being  prepared  in  solution  which  will  keep  unchanged  for  years  (The 
Lancet,  May  14,  1887).  It  consists  of  bismuth  subnitrate,  caustic 
soda  and  potassio-sodium  tartrate.  In  testing  for  sugar  in  urine,  the 
albumen,  if  present,  must  be  first  removed  by  precipitation  by  heat 
and  acid,  and  one  part  of  the  solution  treated  with  ten  of  the  urine, 
when,  if  sugar  is  present,  the  bismuth  will  be  deposited  in  a  metallic 
state.  The  test  is  sufficiently  delicate  to  detect  sugar  in  the  proportion 
of  only  .05  per  cent. 
Pencils  of  iodoform. — Two  kinds  are  employed  by  Poinsot  (Jour,  de 
Med.  de  Paris,  March  6,  1887),  the  soft  variety  being  prepared 
from  equal  parts  of  finely  powdered  iodoform  and  gelatin,  while  the 
hard  pencils  are  composed  of  equal  parts  of  iodoform  and  cacao 
butter. 
Cofee  deodorizing  iodoform. — Coffee  freshly  ground  has  been  rec- 
ommended for  disguising  the  odor  of  iodoform.  Dr.  Neale  (Brit. 
Med.  Jour.,  May  21,  1887)  states  that  its  effects  last  only  for  a  limited 
period,  and  the  coarse  particles  of  the  powder  are  apt  to  irritate  the 
