Am.  Jour.  Pharm.  \ 
Nov.,  1888.  J 
Varieties. 
583 
SOLUBILITY    OF    MAGNESIUM    AMMONIUM  PHOS- 
PHATE IN  ALCOHOL.i 
By  a.  J.  WakejMAnn. 
The  author  mentions  that  Pose,  in  the  sixth  edition  of  his  Handhuch 
der  Analytischen  Chemie,  points  out  that  the  precipitate  of  magnesium 
ammonium  phosphate  is  entirely  insoluble  in  water  containing  one- 
fourth  of  its  bulk  of  ammonia  solution  of  specific  gravity  0*96,  and 
that  under  the  determination  of  phosphoric  acid  by  magnesium  salts, 
Rose  states  that  water  containing  3  per  cent,  of  ammonia  gas  dissolves 
only  traces  of  the  precipitate,  and  that  this  solubility  is  reduced  to  less 
than  half  if  to  the  dilute  solution  of  ammonia  one-fourth  of  its  volume 
of  alcohol  is  added,  and,  further,  that  the  addition  of  alcohol  favors 
the  separation  of  the  precipitate. 
The  author,  in  order  to  test  the  method,  which  he  says  appears  to 
have  been  neglected  by  analysts,  has  made  a  series  of  comparative 
analyses  under  identical  conditions  with  the  exception  that  some  of  the 
precipitates  were  washed  with  ammonia  solution,  according  to  the 
ordinary  method,  and  the  remainder  with  ammonia  solution  containing 
alcohol. 
The  results  of  his  experiments  point  to  a  slight  advantage  in  the 
use  of  alcohol  in  diminishing  the  solubility  of  magnesium  ammonium 
phosphate  when  the  precipitate  is  somewhat  bulky.  The  use  of  alco- 
hol, moreover,  appears  to  make  the  precipitate  more  compact,  so  that 
it  is  more  easily  washed,  and  is  less  liable  to  creep  up  the  sides  of  the 
funnel.  The  addition  of  alcohol  to  the  solution  in  which  the  pre- 
cipitation takes  place  is  not  advantageous,  as  it  causes  the  precipitate 
to  attach  itself  more  closely  to  the  beaker,  so  as  to  be  difficult  of  re- 
moval, and  it  also  retards  the  filtration. 
VARIETIES. 
Caustic  Pencils  are  made  by  De  Sinety  {L' Union  mSd.,  March  17)  of  crys- 
tallized phenol  0.05,  tannin  4.0,  glycerin  5  drops,  and  sufficient  tra^acanth. 
Unguentum  Caldi  chloridi ,  prepared  aS  follows,  is  used  by  Dr.  Lier  {Monatsh. 
/  pr.  Derm.)  in  eczema  :  Ung.  zinci  20,  talc.  5,  ol.  cadinum  5,  calcii  chloridum 
2,  and  water  10  gm. 
1  Technology  Quarterly,  Boston,  i,  173—177 ;  reprinted  from  Jour.  Chem.  Soc, 
October,  p.  1131. 
