172 
Chemical  Notes. 
(  Am.  Jour.  Pliar/ii, 
\      April,  1881. 
It  solidifies  on  cooling  to  a  glass,  which  towards  125°C.  becomes  again 
•crystalline,  and  on  reheating  fuses  only  at  186°  to  187°C. 
Salicin  fuses  at  201°.  When  it  is  heated  just  to  fusion  it  becomes 
-crystalline  on  cooling,  but  if  the  fused  mass  be  heated  for  several  hours 
to  230°  or  240°  w^atery  vapor  gradually  escapes,  and  the  reddish-yel- 
low mass  remaining  consists  in  part  of  saliretin  and  glucosan,  although 
some  undecomposed  salicin  always  remains.  Saligenin  does  not  appear 
to  be  formed. 
Helicin  fuses  at  174°C.,  and  even  at  185°  to  190°C.  gives  very 
little  salicylic  aldehyd.  The  greater  part  is  changed,  as  already 
•observed  by  Piria,  into  a  yellowish  gummy  mass,  which  is  blackened 
.nt  240°C.  and  decomposes  without  previous  fusion.  The  mass,  which 
has  l^een  heated  to  200°C.,  gives,  when  boiled  with  dilute  sulphuric 
acid,  salicylic  aldehyd,  and  the  neutralized  solution  yields  glucosan. — 
Ber.  der  Chem.  Ges.,  xiv,  ]).  303. 
A  New  Modification  of  Helicin. — SchifP  finds  that  pure  crystallized 
helicin,  moistened  with  1  per  cent,  nitric  acid  and  then  dried  for  some 
days  in  the  air,  and  finally  in  an  air-bath  to  110°  to  115°C.,  is 
changed,  without  other  loss  of  weight  than  that  caused  by  the  differ- 
ence of  water  of  crystallization,  into  an  amorphous  modification.  If 
by  washing  with  warm  water  and  then  with  alcohol  the  unchanged 
helicin  is  removed  a  gelatinous  or  pulverulent  white  mass  is  left,  which 
shows  no  crystalline  structure  whatever,  and  after  drying  at  110°C., 
in  vacuo,  yields  no  water.  When  analyzed  it  gave  exactly  the  figures 
for  pure  helicin.  Its  behavior  is,  however,  quite  distinct  from  that  of 
the  ordinary  helicin.  It  is  almost  insoluble  in  water,  alcohol,  cold 
potassium  hydrate  and  glacial  acetic  acid,  in  which  the  normal  helicin 
is  tolerably  soluble.  It  is  not  colored  yellow  by  potassium  hydrate. 
It  does  not  combine  with  ammonia,  while  normal  helicin  forms  a  com- 
pound readily  soluble  in  water  and  alcohol.  Anhydrous  normal  heli- 
<iiu  fuses  at  174°C.,  the  amorphous  becomes  brown  gradually  when 
heated  over  220°C\,  and  decomposes  completely  at  2oO°C.,  without 
previous  fusion.  The  amorphous  helicin  is  decomposed  into  glucose 
and  salicylic  aldehyd,  but  requires,  therefore,  prolonged  heating  with 
10  per  cent,  sulphuric  acid,  while  the  normal  helicin  is  very  easily 
decomposed.  It  can  be  changed  back  to  the  normal  crystallized  heli- 
-cin  easily  when  dissolved  in  warm,  very  dilute  hydrochloric  acid,  from 
which  the  greater  part  will  crystallize  as  normal  helicin  on  cooling. — 
Ibid.,  p.  317. 
