Mar'ch!^9'2o:}        Formula  for  Magma  Magnesia.  1 63 
seemed  possible  to  do  so  without  harmful  effect  on  the  finished 
product. 
This  has  again  led  to  some  work  on  Magma  Magnesia.  This 
preparation  promises  to  become  ever  more  popular  as  time  goes  on, 
and  it  must  be  conceded  that  neither  of  the  two  formulas  that  have 
been  made  official  are  entirely  satisfactory  because  they  involve  too 
great  an  expenditure  of  time,  money,  and  labor.  It  is  not  the 
writer's  object  to  go  further  into  detail  on  this  point  than  to  draw 
attention  to  the  fact  that  the  one  great  drawback  in  these  formulas 
is  the  washing  process.    It  is  costly  and  time-consuming. 
A  pharmacist  must  either  prepare  the  water  for  washing  the  mag- 
ma or  he  must  use  distilled  water.  The  former  involves  time  and 
labor;  the  latter  expense.  Since  pharmacists  usually  buy  their 
distilled  water,  they  would  hardly  feel  that  it  pays  them  to 
use  it  in  such  immense  quantities  as  are  required  for  the  washing  of 
this  preparation.  A  formula,  therefore,  that  does  away  with  this 
washing  process  should  prove  of  considerable  value.  Such  a  formula 
was  advanced  some  years  ago  by  F.  C.  Weber,  who,  according  to 
the  Proc.  of  the  P.  P.  A.,  for  1915,  mentions  Calcined  Magnesia  as 
yielding  a  satisfactory  magma,  and  gives  formula  and  directions  for 
preparing  the  same. 
Light  Magnesium  Oxide  U.  S.  P.  is  without  doubt  a  most  satis- 
factory chemical  for  this  purpose.  It  yields  a  magma  which  stands 
up  splendidly,  does  not  cake  on  long  standing,  pours  easily,  is  beau- 
tifully smooth  and^hite  and  is  free  from  disagreeable  taste.  It 
must  be  remembered,  however,  that  in  order  to  have  good  results 
the  chemical  must  be  of  U.  S.  P.  standard. 
The  simplified  formula  advanced  was  tried  out  by  us  at  the  time ; 
but  it  was  not  wholly  satisfactory  because  of  the  property  possessed 
by  light  magnesium  oxide  to  gelatinize  when  mixed  with  water 
per  se.  This  is  a  disadvantage,  as  the  solidified  mass  thus  formed 
is  not  easily  broken  up  into  a  smooth  magma.  In  order  to  overcome 
this  undesirable  feature,  experiments  were  carried  on  with  water 
containing  a  small  percentage  of  some  chemical.  Various  chemicals 
were  tried  out  in  that  way.  Ultimately  it  was  found  that  lime  water 
U.  S.  P.  was  the  best  solution  for  the  purpose,  as  it  prevents  gelatini- 
zation  and  in  its  stead  brings  about  a  gradual  thickening  of  the  mix- 
ture. 
The  following  formula  has  been  used  by  us  for  some  time  and  has 
always  given  satisfactory  results: 
