252  An  Interesting  Prescription.       {  A™Un°ur^7ann* 
on  order  of  a  physician  by  a  pharmacist.  The  medicine  was  sus- 
pected and  immediately  discontinued.  The  question  naturally  arose 
as  to  whether  or  not  a  mistake  had  been  made  in  compounding  the 
prescription,  which  was  known  to  contain  corrosive  sublimate.  The 
unused  pills  were  turned  over  to  me,  a  friend  of  the  family,  with  a 
view  of  having  the  amount  of  mercuric  chloride  estimated,  so  that 
suitable  treatment  could  be  instituted  if  found  necessary.  A  copy 
of  the  prescription,  which  follows,  was  procured : 
$  Hydrarg.  Bichloride    Grs.  y2. 
Sulphur  Prsecip   Drams  2. 
01.  Theobromae   Q.S. 
Pil.  XXX. 
Sig:  One  before  meals  t.i.d. 
Dr.  
It  will  be  observed  that  this  mixture  calls  for  %0  of  a  grain  of 
corrosive  sublimate,  4  grains  of  sulphur,  and  an  indefinite  amount 
of  cocoa  butter  to  each  pill.  A  number  of  points  must  be  consid- 
ered in  making  an  examination  of  a  mixture  of  this  character. 
First,  variability  in  the  weight  of  the  pills.  Second,  chemical  reac- 
tions which  may  interfere  with  the  estimation  of  the  corrosive  subli- 
mate. Third,  method  of  analysis.  Fourth,  uniform  distribution  of 
the  mercuric  chloride.  These  points  will  be  taken  up  in  the  above 
order. 
First,  variability  of  weight  of  pills.  Twenty  of  the  pills  were 
weighed  with  the  following  results : 
Grams. 
I . 
2. 
3. 
4- 
5. 
6. 
7. 
8. 
9- 
10. 
0.52 
0.50 
0-54 
0-55 
0-53 
0.47 
0.51 
0.52 
0-54 
0-55 
Grains. 
8.0 
11 , 
7-7 
12 
8-3 
13- 
8-5 
14. 
8.2 
15. 
7.2 
16 
7-9 
17. 
8.0 
18 
8.3 
19. 
8-5 
20 . 
Grams. 
Grains. 
0-53 
0-54 
9-59 
0-53 
0.51 
0.56 
0-53 
0.49 
0-55 
0.52 
8.2 
8-3 
9.1 
8.2 
7-9 
8.6 
8.2 
7-6 
8.5 
8.0 
Weight.  Grams.  Grains. 
Maximum    0.59  9.1 
Minimum    0.47  7.2 
Average    0.53  8.2 
Percentage  variation  from  the  average :  2  slightly  exceed  a  10  per  cent, 
variation  from  the  average;  3  exceed  a  5  per  cent,  variation  from  the  average. 
