452 
Analysh'<  of  Wine. 
f  Am  Jour.  Pharm. 
\      Sept.,  1882. 
analytical  methods  which  depend  upon  the  use  of  ])otassiuni  chromate 
as  an  indicator  are  not  available,  because  the  red-brown  silver  cliromate 
is  not  insoluble  in  the  free  acids  of  wine.  The  previous  neutraliza- 
tion of  the  wine  results  in  the  production  of  color  during  the  reaction^ 
which  prevents  the  commencement  of  the  end  reaction  from  being  dis- 
tinguished with  the  necessary  sharpness. 
In  using  Volhard's  method  of  determining  chlorine  white  w  ine  must 
be  first  decolorized  with  animal  charcoal  free  from  chlorine  compounds^ 
as  the  yellow  tannin-like  substances  of  the  wine  will  produce  with  the 
ferric  salt  used  as  an  indicator  an  intensely  dark-green  or  black  color^ 
and  even  by  this  decolorization  the  production  of  color  in  the  wine 
upon  the  addition  of  ferric  salts,  silver  solution  and  potassium  sulpho- 
cyanide  cannot  be  entirely  avoided. 
A  slight  modification  of  Volhard's  method  induces  a  sharp  end  reac- 
tion and  gives  exact  results.  40  to  50  cc.  of  decolorized  wine  is  acidu- 
lated with  nitric  acid  and  treated  with  excess  of  titrated  silver  solution 
and  titrated  solntion  of  potassium  sulphocyanide  added  gradually,  until 
a  drop  of  the  liquid  allowed  to  fall  into  a  drop  of  dilute  solution  of  a 
ferric  salt  (iron  alum)  upon  white  porcelain  shows  a  distinct  red  color.  If 
the  quantity  of  potassium  sulphocyanide  solution  required  be  large,, 
the  experiment  should  be  repeated,  taking  as  small  an  excess  of  silver 
solution  as  possible.  Twenty-five  undoubtedly  genuine  wines  from 
different  districts  (including  five  red  wines)  were  examined  for  chlorine^ 
and  it  was  found  that  the  normal  amount  of  chlorine  in  wine  does  not 
exceed  0*005  per  cent.,  whilst  in  most  wdnes  it  is  below  0*002  per  cent. 
Five  genuine  Markgriifler "  wines,  of  the  years  1822,  1862,  1868, 
1870_,  and  1875,  showed  an  amount  of  chlorine  varying  between  0*002 
and  0*0025  per  cent.  Italian  and  similar  wines,  grown  in  the  neigh- 
borhood of  the  sea-coast,  frequently  yield  an  easily  fusible  ash  that 
does  not  burn  perfectly  white  ;  but  none  have  yet  been  observed  in 
which  the  amount  of  chlorine  exceeded  0.006  per  cent.  At  Carlsruhe 
several  wines  have  been  examined  in  which  the  chlorine  amounted  to 
0*03  per  cent.,  representing  0*05  per  cent,  of  common  salt,  or  25  per 
cent,  of  the  entire  ash. 
IV.  Deteetion  of  Free  Tartaric  Acid  in  Wine. — If  100  cc.  of  wine 
be  evaporated  to  a  thin  syrup,  and  this,  while  kept  stirred,  be  treated 
with  stronsT  alcohol  until  a  fresh  addition  of  spirit  no  longer  causes 
precipitation,  all  the  tartar  will  separate  within  two  hours  and  the 
alcoholic  solution  will  contain  the  free  tartaric  acid.    The  alcohol  is. 
