602 
Tubular  Prismatic  Crystals. 
/Am.  Jour.  Pharm. 
X  December,  1895. 
cipitate  the  copper,  for  in  all  cases  the  supernatant  liquid  possessed 
a  green  color.  It  having  thus  been  proven  that  none  of  the  samples 
were  of  full  official  strength,  sufficient  of  the  sample  was  added  to 
supply  the  deficiency  and  fulfil  the  indication  of  complete  precipita- 
tion, in  order  to  ascertain  the  exact  amount  of  calcium  monosul- 
phide  present. 
The  quantity  required  for  this  purpose  was  determined  by  supply- 
ing it  from  a  known  weight  and  deducting  from  this  the  weight  of 
the  unused  portion. 
The  table  gives  the  amount  in  grammes  of  each  sample  needed 
for  the  official  test,  as  also  the  corresponding  percentage  content  of 
calcium  monosulphide. 
Sample. 
Amount  Required. 
Percentage  of  Calcium 
Monosulphide. 
U.  S.  P. 
I  "OCX) 
60 -oo 
i 
1-277 
45'52 
2 
44-45 
3 
2-358 
24-85 
4 
1-386 
41-59 
5 
1-621 
35  73 
Sample  No.  5  was  received  wrapped  in  three  papers ;  the  middle 
one  was  parchment  paper.  The  other  samples  were  in  small  cork- 
stoppered  vials,  sealed  with  paraffin  and  capped  with  foil. 
Sample  No.  3  was  not  claimed  by  the  manufacturer  (who  was 
aware  that  this  comparison  was  to  be  made)  to  be  the  official  sub- 
stance, but  merely  a  crude  calcium  sulphide,  li  we  exclude  this 
sample  on  account  of  what  has  just  been  said,  we  still  have  the 
remaining  four,  showing  percentages  nearer  to  36,  the  amount 
ordered  by  the  Pharmacopoeia  of  1880,  than  to  the  60  per  cent,  at 
present  required. 
TUBULAR  PRISMATIC  CRYSTALS.  — _ 
By  I^yman  F.  Kebeer. 
Monobromated  camphor  furnishes  us  with  crystals  of  at  least  two 
particular  habits,  prisms  and  scales.    Exactly  what  it  is  that  deter- 
mines the  habit  of  a  crystal  is  not  known.    Experiments  appear  to 
indicate  that  impurities  exert  a  powerful  influence  on  the  forms  of 
