AmoJc°tu,r'i8P76?rm'}     Metrical  Weights  in  Prescriptions.  46 1 
to  rather  less  than  a  plus  of  if  grain  for  the  drachm,  and  14  grains  for 
the  troyounce. 
A  few  examples  may  yet  be  added  to  show  the  insignificance  of  this 
difference  for  smaller  weights  ;  thus  we  obtain  for — 
Actual 
Difference. 
weight. 
Gram.  Grain. 
grs 
x, 
1 0 
IT 
=  o-66 
0-648 
.0-012  less  than  | 
grs. 
viii, 
tV 
=  o'53 
C518 
0-012           "  ^ 
grs. 
in, 
3 
13" 
=  0*20 
0794 
0-006       "  yq 
grs. 
i5> 
2 
T3" 
=  0'13 
0-129 
o'oox    nearly  g1^ 
grs. 
>> 
1 
TT 
=  o*o66 
0*065 
o-ooi       "  JT 
In  prescribing  by  metrical  weights,  the  amounts  should  in  all  cases 
be  expressed  in  grams  and  decimal  fractions  of  grams,  and  with  Arabic 
numerals,  in  which  case  no  signs  or  abbreviations  are  required  ;  a  few 
examples  of  prescriptions,  written  in  the  usual  manner,  with  their 
(practical)  equivalents  in  metrical  weights,  will  readily  explain  this,  and 
show  the  greater  clearness  of  the  latter  method,  and  the  less  liability 
to  error  from  indifferently  made  signs  and  Roman  numerals. 
R.    Potassii  iodidi,                .              .              .  8  00 
Iodinii,     .              .               .               .  gr.  ii  0-13 
Aquae,             ....  fjfss  15*00 
Syr.  sarsap.  comp ,  .              .              .  f^iiiss  140*00 
Dose. — One  tablespoonful,  containing  one  gram  (15  grains)  potassium  iodide, 
and  0*016      gr.)  iodine. 
R.    Potassii  nitrat.,               .              .              .  ^iss  6*oo 
Vin.  antim,,             .              .             .  .  rn^xl  2*66 
Tinct.  digitalis,              .              .              .  f^i1  3*50 
Mucil.  acacias,         .  '            .              .  f^ss  20*00 
Aquas,            ....  ffiii  90*00 
Syrup,  aurantii,       .              .              .  f^i  40*00 
A  tablespoonful  of  this  mixture  contains  o'66  (10  grains)  of  potas- 
sium nitrate,  0*0012  (-^  grain)  tartar  emetic,  and  0*055  (j  grain)  digi- 
talis. 
R.    Morphias  sulphat.,  .  .  .    gr.  i  0-066 
Pulv.  digitalis,  .  .  gr.  vi  0*40 
Sacchari  albi,   ....    ^iss  2-00  M, 
Divide  in  chart.  No.  12. 
Each  powder  contains  0*0055  (A  gram)  morphia,  and  0*033  (i  grain) 
digitalis. 
1  Representing  7^  grains  of  digitalis;  menstruum  diluted  alcohol. 
