AS!teeU!;m2?M'}        Precipitation  of  Silver  by  Copper.  551 
neous  nerves,  it  completely  removes  and  prevents  the  morbid  itching, 
prurigo  and  pruritus.  In  case  of  prurigo  and  pruritus,  independent 
of  itch,  the  internal  use  of  carbolic  acid  in  the  form  of  pills  is  an  ex- 
cellent remedy.  As  the  carbolic  acid  gets  pretty  quickly  into  the 
circulation,  it  is  necessary  to  give  it  in  very  moderate  doses,  especial- 
ly where  there  are  parts  destitute  of  epidermis.  But  as  thereby  its  ac- 
tion is  delayed,  it  is  better  to  employ  the  carbolic  acid  in  the  form  of 
a  salt.  According  to  Rothmund,  natrum  carbolicum  supplies  all  the 
requirements  of  a  good,  rapid  and  certain  itch  remedy.  The  follow- 
ing is  the  best  way  of  using  it : — 
R.       Natr.  carbol.,      -       -  ^xv. 
Aqua  destil.,  -  -  flozclxxx.  M. 
With  this  the  affected  portions  of  the  skin  are  to  be  rubbed  three 
times  a  day,  and  even  in  the  most  inveterate  cases  the  treatment 
never  lasts  more  than  two  and  a  half  days  ;  relapses  are  not  to  be 
feared,  and  if  the  rubbing-in  is  carefully  performed,  no  erythema  to 
speak  of  occurs.  During  the  treatment  the  patients  are  in  no  way 
hindered  from  following  their  usual  occupations.  One  advantage  of 
the  Peru  balsam  and  carbolic  acid  treatment  of  itch  is  that  it  is  not 
necessary  to  disinfect  the  clothes  or  bed  linen.  In  order  to  make 
sure,  Rothmund  recommends  an  additional  rubbing-in  to  be  made 
some  eight  or  ten  days  after  the  cure  of  the  itch,  in  order  to  kill  any 
acari  or  their  eggs  that  may  have  lurked  among  the  clothes  or  bed 
linen. — Canadian  Pharm.  Journal,  Oct.,  1872. 
THE  PRECIPITATION  OF  SILVER  BY  COPPER.* 
By  Alfred  Tribe,  F.C.S. 
f  When  a  piece  of  copper  foil  is  metallically  connected  into  a  piece 
of  silver,  and  placed  into  an  aqueous  solution  of  cupric  nitrate  (dilute 
to  about  6  per  cent.)  containing  air,  the  oxygen  of  the  latter  slowly 
combines  with  the  copper  of  the  nitrate,  forming  cuprous  oxide,  which 
deposits  on  the  silver  in  a  fine  crystalline  condition,  whilst  the  nitric 
element  combines  with  metallic  copper,  reproducing  the  nitrate.  If 
the  copper  have  its  surface  covered  with  crystalline  silver,  the  decom- 
position of  cupric  nitrate  by  free  oxygen  is  accelerated,  so  much  so 
that,  when  this  couple  is  moistened  with  the  salt  and  exposed  to  air 
*  Read  before  the  British  Association,  Brighton  Meeting,  Section  B. 
