348 
CARBONATE  AND  OXIDE  OF  SILVER. 
ON  THE  SUBSTITUTION  OF  THE  CARBONATE  FOR  THE  OXIDE 
OF  SILVER  IN  COMMERCE. 
By  Mr.  John  Borland. 
At  the  present  time,  when  attention  is  so  properly  directed  to 
the  detection  and  exposure  of  adulterations  and  impurities  in  many 
substances  used  in  dietetics  and  medicine,  I  beg  to  be  allowed  to 
draw  attention  to  the  existence  of  a  fraud  which  appears  to  me  to 
be  very  generally  practised  with  a  medicine  that  is  now  come  into 
extensive  use  as  a  tonic  in  dyspepsia  and  other  complaints  of  the 
digestive  organs.  I  allude  to  the  substitution  of  carbonate  of  silver 
for  oxide  of  silver. 
I  have  carefully  examined  several  specimens,  all  purchased  from 
different  respectable  wholesale  druggists  in  London,  and  have 
found  that  each  of  them,  besides  being  contaminated  with  the 
oxides  of  copper,  lead,  and  iron,  contained  a  large  portion  of 
carbonic  acid,  and  effervesced  strongly  when  thrown  into  diluted 
nitric  acid. 
As  none  of  the  specimens  were  wholly  soluble  in  liquor  of  am- 
monia, but  contained  a  considerable  quantity  of  some  substance 
insoluble  in  this  menstruum,  I  was  lead  to  suppose  that  the  evolu- 
tion of  the  carbonic  acid  might  be  due  to  the  presence  of  some 
earthy  or  alkaline  carbonate  that  had  been  added  by  way  of  adul- 
teration. This,  however,  after  close  examination,  I  found  not  to 
be  the  case,  so  that  the  effervescence  could  not  be  accounted  for  in 
any  other  way  than  by  supposing  the  carbonic  acid  to  be  combined 
with  the  oxide  of  silver. 
That  it  was  carbonic  acid,  I  satisfied  myself  by  holding  a  watch- 
glass  moistened  with  lime  water  above  the  effervescing  solution, 
when  a  thin  whitish  film  of  carbonate  of  lime  was  visibly  and 
quickly  formed.  I  also  passed  the  acid  into  a  solution  of  pure 
caustic  potass,  and  on  afterwards  testing  the  solution,  found  it  to 
contain  carbonate  of  potass. 
In  the  preparation  of  this  sophisticated  article,  the  manufacturer, 
I  suspect,  has  employed  a  solution  of  the  carbonate  of  some  one 
of  the  fixed  alkalies,  in  place  of  its  caustic  solution,  to  precipitate 
the  oxide  of  silver. 
The  product  yielded  by  this  process  is  consequently  greater,  as 
it  contains  the  additional  weight  of  the  carbonic  acid  with  which 
