218 
Chemical  Notes. 
f  Am.  Jour.  Pb  arm, 
\      May,  1882. 
the  contents  of  the  flask  appear  to  consist  of  a  crystalline  cake,  soakecT 
with  a  reddish  liquid.  There  is  then  added  93  per  cent,  alcohol,  and 
the  whole  is  shaken  up  until  on  farther  addition  no  precipitate  sepa- 
rates out.  The  separated  Glauber's  salt  is  separated  from  the  alco- 
holic solution  by  a  vacuum  filter,  and  can  be  washed  with  relatively 
very  little  alcohol.  The  half  of  the  alcoholic  solution  is  neutralized 
over  the  water-bath  with  carbonate  of  zinc,  filtered  boiling  hot,  and 
united  with  the  other  half.  The  crystallization  begins  immediately 
upon  cooling,  and  is  complete  after  36  hours'  standing.  The  lactate 
of  zinc  so  obtained  can  be  pressed  free  from  mother-liquor  and 
recrystallized  once,  when  it  is  perfectly  pure.  The  weight  of  this  first 
crystallization  amounts  to  30  to  40  per  cent,  of  the  sugar  used.  The 
concentrated  mother-liquor  yields  yet  another  portion  of  crystals^ 
which  are  nearly  pure,  although  slightly  yellowish  in  color. — Ber. 
Chem.  Ges.,  xv,  pp.  136  and  699. 
Test  for  Natural  Vegetable  Gums. — C.  Reichl  and  F.  Breinl  give 
the  following  test  for  arabin  and  bassorin  as  distinguished  from  dex- 
trin or  artificial  gum.  The  former  two,  when  heated  with  hydro- 
chloric-acid and  orcin,  give  a  blue  flocculent  mass,  which  with  alco- 
holic potash  yields  a  violet  solution,  fluorescing  green.  This  reaction 
is  shown  by  wood  gum  so  easily  that  even  fragments  of  wood,  which 
contain  traces  only  of  gum,  when  boiled  with  orcin  and  hydrochloric 
acid,  show  the  reaction  quite  distinctly. —  Chem.  Industrie,  Feb.,  1882, 
p.  51. 
Change  of  Xanthine  into  Theobromine  and  Caffeine. — Xanthine  has 
the  composition  C5H4N4O2,  and  differs  from  theobromine,  C^H-gN^Oa, 
by  having  2  carbon  and  4  hydrogen  atoms  less.  Strecker  already  sug- 
gested that  the  second  base  might  be  a  dimethyl  derivative  of  the  first. 
This  view  had  not,  however,  been  hitherto  substantiated  by  experi- 
ment. Emil  Fischer  has  now  established  this  fact  by  converting 
xanthine  into  theobromine,  and  this  then  into  caffeine.  He  accom- 
plished this  by  dissolving  xanthine  in  caustic  soda  solution,  and  then 
precipitating  by  acetate  of  lead,  whereby  he  got  a  white  crystalline 
xanthine  lead.  This  salt,  dried  at  130°C.,  was  heated  with  1\  times 
its  weight  of  methyl  iodide  in  closed  tubes  for  12  hours  to  100°C. 
The  contents  of  the  tube,  which  are  nearly  dry,  are  boiled  with  water, 
freed  from  remaining  lead  by  hydrogen  sulphide,  and  after  saturation 
with  ammonia  evaporated  to  crystallization.  There  is  obtained  in  this 
way  a  slight  yellowish  crystalline  powder,  which  on  analysis  proved 
