354  Gleanings  from  the  European  Journals,  {AMAugURi,  lS"' 
caoutchouc.  If  applied  with  a  brush  to  the  corks  used  for  the  appa- 
ratus for  preparing  chlorine,  the  joints  are  perfect. — Archiv  d. 
Bharm.,  May,  151. 
New  Reagent  for  Blood. — H.  Struve  found  that  the  coloring  mat- 
ter of  blood  is  best  precipitated  in  the  following  manner  :  To  the 
liquid  containing  blood,  a  little  ammonia  or  caustic  potassa  is  added, 
then  a  solution  of  tannin,  and  finally  acetic  acid,  until  the  reaction  is 
distinctly  acid.  The  dark-colored  precipitate,  tannate  of  hsematin, 
subsides  rapidly,  is  easily  collected,  washed  and  dried,  and  yields, 
when  treated  with  sal  ammoniac  and  glacial  acetic  acid,  the  well-known 
haemin  crystals. 
20  c.  c.  of  urine  containing  0*023  per  ct.  blood  yielded  an  abundant 
precipitate,  sufficient  for  many  experiments  for  haemin. — Zeitschr.  f. 
Anal  Chem.,  1872,  29. 
A  source  of  Error  in  the  Estimation  of  Sugar  with  Fehling's  Solu- 
tion has  been  pointed  out  by  Dr.  L.  Brunner,  who  found  that  some 
kinds  of  filtering  paper  are  very  appreciably  dissolved  by  alkaline  so- 
lutions of  copper ;  he,  therefore,  recommends  to  ascertain  this  beha- 
viour of  the  copper  solution  for  each  lot  of  filtering  paper,  or  to  con- 
vert the  cuprous  oxide  obtained  in  the  process  into  cupric  oxide. — 
Ibid.  32. 
Examination  of  Indigo. — It  is  uncertain  whether  the  presence  of 
the  other  constituents  of  indigo  besides  the  blue  coloring  matter,  does 
not  render  the  estimation  of  the  latter  by  the  oxidation  process  in- 
correct, or  at  least  uncertain.  J.  Loewenthal  believes  that  more  re- 
liable results  are  obtained  from  estimating  the  ashes,  which  sometimes 
amount  to  29  per  ct.,  while  an  excellent  indigo  yielded  only  4-5  per  ct. 
—Ibid.  45. 
Modification  of  Bettenkofers  Test  for  Biliary  Acids. — Strassburg* 
adds  to  the  urine  to  be  tested  a  little  cane  sugar,  then  moistens  a 
piece  of  filtering  paper  with  the  liquid,  and,  after  drying,  places  a 
drop  of  concentrated  sulphuric  acid  upon  the  impregnated  paper, 
which  after  J  minute  shows  the  violet  coloration  beautifully,  particu- 
larly in  transmitted  light.  Normal  urine  does  not  produce  this  color- 
ation, which  appears  if  only  0*00003  biliary  acids  are  present. — 
Ibid.,  91. 
*  Archiv  d.  Physiol,  iv,  461. 
