220 
Analytical  Researches  and  Investigations. 
f  Am.  Jour.  Pharm. 
X      ."May,  1882. 
able  acids  at  all,  renders  the  existence  of  the  latter  as  belonging  to  the 
integral  constituents  of  the  Maracaibo  balsam  somewhat  problematical. 
The  product  which  is  furnished  by  the  German  chemical  manufactories 
as  metacopaivic  acid  and  copaivic  acid,  is  not  obtained  from  copaiba 
balsam,  but  from  gurgun  balsam,  and  is  not  identical  with  Werner's 
gurgunic  acid  which,  according  to  Strauss,  is  the  same  as  metacopaivic 
acid.  Both  of  the  products  which  occur  in  trade  melt  at  126  to  129°C., 
dissolve  in  ether  and  alcohol,  even  that  of  80  per  cent.,  and  are  pre- 
cipitated from  the  alcoholic  solution  bv  water  in  the  form  of  beautiful, 
long  needles,  with  a  silky  lustre.  Although  the  obtained  formula 
agrees  perfectly  with  that  of  copaivic  acid,  C20H3QO2,  as  determined  by 
the  analyses  of  Rose  and  Hess,  yet  its  want  of  solubility  in  ammonia, 
as  also  of  all  acid  properties,  excludes  its  identity  with  the  copaivic  acid 
of  older  authors.  The  successful  obtainment  of  an  an  acetyl  product 
points  to  the  rational  formula  C2oH28,OH2. — Pharm.  Zeitung,  No.  16. 
p.  116,  1882,  from  Sitzungsberichte  d.  Acad.  d.  Wiss.  zu  Wien^ 
'No.  6,  p.  459, 1881. 
Permanent  Solution  of  Litmus. — Various  formulas  have  from  time 
to  time  been  proposed  in  the  journals  for  obtaining  a  permanent  litmus 
solution,  which  appear,  however,  more  or  less  circumstantial.  The 
author  gives  a  method  for  obtaining  a  solution  which  may  be  pre- 
served for  months  in  a  vessel  closed  with  paper,  or  even  with  a  cork. 
The  litmus  solution  is  first  prepared,  according  to  the  suggestion  of 
Mohr,  "  Lehrbuch  der  chem.-analyt.  Titrirmethode  "  p.  73,  and  subse- 
quently evaporated  at  a  temperature  of  90°C.  to  dryness  ;  if  the  ob- 
tained residue  is  then  dissolved  in  a  little  glycerin,  a  solution  is 
obtained  which  remains  permanent  for  months,  and  its  sensibility  is  in 
no  wise  influenced.  By  its  application  it  is  only  necessary  to  dip  a 
glass  rod  into  the  solution,  which  amount  suffices  for  tinting  any 
required  amount  of  liquid. — H.  K.  Ibid.,  p.  117. 
Detection  of  Ilercury  in  Liquids. — Prof.  Merget,  in  Bordeaux,  recom- 
mends the  following  very  simple  procedure  for  the  detection  of  mer- 
<3ury  in  liquids.  A  bright  rod  of  copper,  or  a  copper  plate,  is  dipped 
into  the  liquid  to  be  examined,  and  allowed  to  remain  therein  the 
longer,  the  smaller  the  amount  of  mercury.  A  strip  of  paper  is  pre- 
viously prepared,  by  rubbing  it  with  cotton,  which  has  been  impreg- 
nated with  an  ammoniacal  solution  of  nitrate  of  silver,  and  subsequently 
allowed  to  dry.  The  copper  plate  is  then  removed  from  the  liquid, 
dried  by  pressing  it  between  bibulous  paper,  and  enclosed  in  doubly 
