602  Influence  of  Gum  Arabic  in  Reactions,  {^°'d°"'i882*™' 
of  water  and  20  cc.  indigo  solution^  and  titrated  with  potassium  per- 
manganate. By  deducting  from  the  quantity  of  potassium  permanga- 
nate used  in  the  direct  titration  the  quantity  consumed  in  the  second 
titration  the  number  of  cubic  centimeters  required  to  oxidize  the 
tannic  acid  in  10  cc.  of  infusion  is  obtained.  As  the  vohmie  corres- 
ponding to  a  certain  weight  of  extracted  material  is  known,  and  the 
potassium  permanganate  vahie  of  the  tannin  has  been  determined  pre- 
viously, it  is  easy  to  calculate  the  percentage  of  tannin  in  the  tanning 
materials,  provided  that  in  the  gelatin  filtrate  the  "  non-tannin  bodies 
only  are  titrated.  This,  however,  was  found  not  to  be  the  case.  The 
consummation  of  potassium  permanganate  in  titrating  the  gelatin  filtrate 
is  mainly  due  to  the  solubility  of  the  "  gelatin  tannate  "  in  dilute  sul- 
phuric acid.  The  author  is  investigating  this  point  with  a  view  of 
remedying  it. — Jour.  Chem.  Soc,  Nov.,  1882;  from  Dingl.  Polyt.  J.^ 
244,  303-411. 
THE  INFLUENCE  OF  GUM  ARABIC  IN  CERTAIN 
CHEMICAL  REACTIONS. 
By  J.  Lefort  and  P.  Thibault. 
It  is  known  that  the  presence  of  certain  organic  substances  in  saline 
solutions  may  prevent  the  formation  of  a  large  number  of  precipitates. 
In  this  respect  the  influence  of  tartaric  acid  is  familiar  to  chemists.. 
The  researches  it  is  proposed  to  describe  warrant  the  statement  that 
some  neutral  bodies,  and  gum  arable  in  particular,  also  enjoy  this 
property. 
Upon  this  principle  is  based  the  therapeutic  employment  of  soluble 
sulphide  of  mercury,  as  described  by  M.  Lambron  in  a  communica- 
tion to  the  French  Academy  of  Medicine.  M.  Lambron  pointed  out 
that  wdien  an  aqueous  solution  of  bichloride  of  mercury  is  added  tO' 
the  sulphuretted  Luchon  water  a  precipitate  of  sulphide  of  mercury  is- 
rapidly  formed,  which  falls  to  the  bottom  of  the  vessel  as  a  black 
powder.  But  if,  instead  of  introducing  the  bichloride  of  mercury 
directly,  it  be  previously  mixed  with  syrup  of  gum  or  sarsaparilla,. 
beef  tea,  albumen  or  apple  jelly,  and  then  poured  into  the  Luchon 
water,  in  proportion  a  little  in  excess  of  the  sulphur  strength  of  the 
water,  no  precipitate  is  formed,  even  after  several  weeks  of  contact. 
This  observation  induced  M.  Lambron  to  suppose  that  when  bichlo- 
ride of  mercury  is  dissolved  and  mixed  with  gummy  and  albuminous 
