536    SOLUBILITY  OP  GOLD  IN  NITRIC  AND  SULPHURIC  ACIDS. 
added  to  prevent  any  slight  precipitation  that  might  otherwise 
occur  when  the  wine  was  exposed  to  strong  sunlight.  The 
formula  proposed  was  as  follows  : — 
Ammonia-citrate  of  Iron  160  grains. 
Crystalline  Citrate  of  Ammonia     .    .     60  " 
Sherry   1  pint. 
The  wine  thus  prepared  was  perfectly  transparent,  and  had  no 
disagreeable  taste  London  Pharm.  Jour,  for  October. 
ON  THE  DETERMINATION  OF  WATER  IN  ORGANIC  SUB- 
STANCES. 
By  M.  Cl.  Winckler. 
This  determination  is  founded  on  the  change  of  color,  which 
anhydrous  chloride  of  cobalt  undergoes  in  absorbing  water. 
Dry  chloride  of  cobalt  dissolves  in  alchol  of  a  density  of  0*792, 
preserving  a  beautiful  blue  color.    Hydrated  bodies,  in  presence 
of  this  solution,  abandon  their  water,  and  the  color  turns  to  red. 
The  operation  is  begun  by  titrating  the  solution  of  cobalt,  to  as- 
certain the  quantity  of  it  which  must  be  added  to  a  certain 
amount  of  water  to  produce  a  fixed  color.    In  this  way  the  au- 
thor has  determined  the  alcoholic  strength  of  mixtures  of  alcohol 
and  water.    London  Chemical  News,  from  Bulletin  de  la  jSo- 
ciete  Chimique,  vi.  460,  64. 
ON  THE  SOLUBILITY  OF  GOLD  IN  NITRIC  AND  SULPHURIC 
ACIDS. 
To  the  Editor  of  the  Chemical  News. 
Sir, — Since  sending  you  the  note  on  the  solubility  of  gold,  a 
chemist  of  my  acquaintance  has  informed  me  that  the  informa- 
tion given  was  not  sufficient  to  enable  him  to  perform  the  ex- 
periment satisfactorily.  I  therefore  send  you  a  more  complete 
account  of  the  experiment  performed  by  me. 
The  alloy  of  silver  and  gold  was  exposed  to  the  action  of 
nitric  acid  until  the  gold  was  left  in  a  powder.  On  heating  this 
powder  with  sulphuric  acid  a  yellow  solution  was  obtained, 
which,  when  poured  into  water,  gave  a  purple  precipitate.  This 
at  first  led  me  to  suppose  that  the  sulphuric  acid  had  dissolved 
