486  Formula  for  Incr  easing  and  Reducing  {'^"'•noT'Xs^'"'' 
Knowing  that  chloride  of  lead  in  acid  solution  is  not  precipitated  by- 
sulphuric  acid,  and  that,  therefore,  sulphuric  acid  can  be  in  muriatic 
acid  besides  chloride  of  lead  ;  I  was,  nevertheless,  astonished  that  from 
the  acid,  by  dilution  as  well  as  by  evaporation,  only  chloride  of  lead 
and  no  sulphate  of  lead  was  precipitated. 
By  saturating  chem.  pure  hydrochloric  acid  with  fresh  precipitated 
sulphate  of  lead,  of  which  about  four  per  cent,  were  taken  up  at  com- 
mon temperature,  an  acid  was  obtained  which  acted  exactly  in  the 
same  way  as  the  commercial  acid  in  question,  that  is,  by  dilution  with 
water  and  also  by  evaporation  only  pure  chloride  of  lead  was  obtained, 
from  which  fact  the  inference  has  to  be  drawn,  that  the  sulphate  of 
lead  is  not  dissolved  as  such  in  hydrochloric  acid,  but  that  it  is  converted 
into  chloride  of  lead. 
The  solution  of  perchloride  of  iron  being  freed  from  the  crystals  of 
chloride  of  lead,  gave,  by  mixing  with  three  parts  of  alcohol,  another 
precipitate  of  crystals  of  chloride  of  lead.  The  alcoholic  solution  con- 
tained yet  traces  of  lead,  and  all  the  iron  solution  had,  of  course  to  be 
rejected  for  pharmaceutical  use. 
Louisville,  August,  1875. 
FORMULA   USEFUL    FOR    INCREASING   AND    REDUCING  THE- 
STRENGTH  OF  LIQUIDS  TO  A  DESIRED  DEGREE. 
BY   EDO  CLAASSEN. 
I.  We  have  on  hand  a  liquid,  the  weight  and  percentage  of  which 
we  know.  We  want  to  mix  it  with  so  much  of  a  liquid  of  the  same 
kind,  but  of  higher  or  lower  percentage,  or  with  so  much  water  that 
the  mixture  will  exactly  have  the  desired  percentage. 
If  we  call 
a — the  quantity  of  the  liquid  on  hand,  of  known  percentage  ; 
b — its  percentage  ; 
c — the  percentage  of  the  liquid  to  be  mixed  with  a  ; 
d — the  desired  percentage  of  the  mixture  ; 
X — the  quantity  of  the  liquid  to  be  mixed  with  a  of  higher  or  lower 
percentage,  or  the  quantity  of  water,  we  have 
i)  x=^^^ — ^,  if  a  liquid  of  the  same  kind,  but  of  higher  or  lower 
percentage  must  be  added  ;  or,  in  words  : 
To  find      the  quantity  of  the  liquid  to  be  added  of  higher  or  lower 
