164 
Formula  for  Magma  Magnesia. 
Am.  Jour.  Pharm. 
March,  1920 
Light  Magnesium  Oxide,  U.  S.  P   60.00 
Lime  Water,  U.  S.  P.  to  make   1000.00 
Gradually  and  with  constant  stirring  add  the  light  magnesium 
oxide  to  about  800  Mils,  of  lime  water  contained  in  a  graduate  or  a 
graduated  wide  mouthed  jar.  Mix  thoroughly  and  bring  up  to  1000 
Mils,  with  lime  water,  then  pour  into  a  bottle  of  the  capacity  of  about 
two  liters.  Stopper  the  bottle  and  shake  vigorously,  at  frequent 
intervals,  until  the  mixture  has  thickened  properly. 
It  has  been  our  experience  that  vigorous  shaking  at  frequent 
intervals  hastens  thickening  of  the  magma.  This  is  especially  true 
if  a  bottle  is  used  that  holds  considerably  more  than  the  amount  of 
magma  to  be  manufactured.  If  these  requirements  are  carried 
out  a  splendid  magma  can  be  prepared  within  three  days'  time. 
It  does  seem  strange,  but  it  is  a  fact  that  rubbing  the  magma  up 
in  a  mortar  does  not  hasten  its  thickening  nor  is  the  finished  product 
in  any  way  superior  to  the  one  prepared  according  to  above  direc- 
tions. 
Another  thing  that  might  prove  of  interest  is  the  corking  of 
magma  magnesia.  It  is  common  knowledge  that  ordinary  corks  are 
quickly  acted  upon  by  the  alkaline  mixture,  causing  them  to  turn 
dark,  with  the  result  that  the  magma  is  stained  dark  where  it  comes 
in  contact  with  the  cork.  This  unsightly  appearance  in  the  neck 
of  the  bottle  can  be  avoided  if  the  cork  is  given  a  protective  coating 
of  parafiine  previous  to  its  use.  A  cork  thus  protected  can  be  used 
for  months  without  causing  the  slightest  discoloration. 
It  may  be  stated  that  though  this  chemical  is  much  more  expen- 
sive than  magnesium  sulphate,  the  quantity  required  for  one  liter  of 
the  preparation  does  not  cost  more  than  the  sum  total  of  the  chem- 
icals that  enter  into  the  same  amount  of  magma  prepared  according 
to  either  of  the  formulas  that  have  been  officially  recognized. 
This  striking  fact  was  brought  out  by  an  estimate  made  according 
to  a  price  list  for  February,  1920,  issued  by  a  large  chemical  manu- 
facturing firm.  According  to  this  price  list,  the  cost  of  the  chemicals 
for  one  liter  of  magma  magnesia,  U.  S.  P.  formula,  amounts  to 
from  twelve  and  one-half  to  thirteen  cents.  The  cost  of  the  chemi- 
cals according  to  the  N.  F.  formula  amounts  to  about  fifteen  cents, 
and  that  of  the  formula  given  above  to  about  twelve  and  one- 
half  cents.  From  this  it  can  readily  be  seen  that  the  distilled  water 
required  for  washing  the  magma  comes  very  much  higher  than  the 
chemicals  do. 
