Am.  Jour.  Pharru. ) 
August,  1906.  / 
The  U.S. P.  Inorganic  Chemicals. 
393 
There  are  also  great  discrepancies  if  the  determinations  are  car- 
ried out  by  the  cooling  of  a  hot  saturated  solution. 
Aqua. — From  the  standpoint  of  the  chemist,  the  framing  of  tests 
for  the  exclusion  of  sewage  contamination  from  Aqua  U.S.?.,  is  a 
very  unsatisfactory  task.  For  at  times  it  requires  the  highest  skill 
on  the  part  of  the  chemist  to  detect  certain  kinds  of  contamination  by 
chemical  tests,  in  fact  a  bacteriological  examination  is  more  to  be 
relied  on  than  the  former.  However,  since  it  is  the  chief  object  of 
the  Pharmacopoeia  to  exclude  such  waters  as  are  grossly  con- 
taminated, the  revised  tests  will  in  careful  hands  accomplish  this 
object. 
Aqua  Destillata. — The  tests  for  ammonia  were  omitted,  owing  to 
the  readiness  with  which  this  gas  is  taken  up  by  distilled  water 
when  handled  about  the  store.  The  presence  of  traces  (more  or 
less)  of  ammonia  would  have  no  bearing  on  the  purity  of  distilled 
water  anyhow. 
Because  of  the  solubility  of  the  glass  of  containers  in  distilled 
water,  we  must  permit  the  presence  of  soluble  matter ;  this  was  not 
recognized  in  the  last  revision  and  caused  hardships  in  the  enforce- 
ment of  our  pharmacy  laws. 
This  solubility  of  glass  in  water  varies  considerably,  according  to 
the  nature  of  the  glass,  thus:  ioooc.c.  of  distilled  water  stored  for 
one  month  in  a  green  glass  bottle  gave  a  residue  weighing  14  milli- 
grammes; another  like  volume  stored  in  an  amber  bottle  gave  58 
milligrammes  of  residue;  stiil  another  sample  of  1000  c.c.  gave  no 
weighable  residue  after  storing  for  one  month's  time.  One  liter  of 
distilled  water  when  boiled  for  two  hours  in  a  Bohemian  flask,  took 
up  only  20  milligrammes  of  residue,  while  American  colorless 
chemical  glass  gave  up  24  milligrammes  of  soluble  matter  under 
like  conditions. 
Ordinary  water  containing  75  milligrammes  per  liter  can  scarcely 
pass  the  U.S. P.  tests  for  distilled  water,  hence  such  a  substitution  is 
not  probable. 
Arseni  Iodidum. — The  commercial  impure  article,  prepared  by 
fusing  metallic  arsenic  and  iodin  together,  is  of  variable  iodin  con- 
tent, and  in  an  unsatisfactory  state  for  defining  limits  of  purity. 
But  if  the  pure  compound  be  prepared  by  dissolving  10  c.c.  of 
arsenous  oxid  in  250  c.c.  of  hot  hydrochloric  acid  and  pouring  into 
a  solution  of  51  grammes  of  potassium  iodid  in  40  c.c.  of  warm 
