450  CONVERSION  OF  MANNITE  AND  GLYCERINE  INTO  SUGAR. 
cipitate  formed  must  contain  the  chlorine,  bromine,  and  iodine 
of  the  water.  It  is  washed  and  carefully  dried.  It  is  then 
intimately  mixed  with  a  little  cyanide  of  silver  and  introduced 
into  a  tube,  at  one  end  of  which  it  is  fixed  between  two  plugs 
of  wadding  and  abestos.  A  current  of  very  dry  chlorine  is 
then  passed  slowly  over  the  mixture,  whilst  the  corresponding 
part  of  the  tube  is  slightly  heated.  The  iodine,  bromine,  and 
cyanogen  are  displaced,  combine  and  condense  in  the  colder 
parts  in  the  form  of  a  white  crystalline  ring  of  iodide  and 
bromide  of  cyanogen.  The  tube  is  then  closed  at  both  ends,  and 
may  serve  in  case  of  need  as  a  piece  of  evidence. 
The  physical  and  chemical  properties  of  iodide  and  bromide 
of  cyanogen  do  not  allow  them  to  be  confounded  with  other  com- 
pounds. The  iodide  sublimes  at  113°,  and  the  bromide  at  59°F. 
This  allows  them  to  be  separated  mechanically  by  plunging  the 
tube  into  water  at  86°F.  The  iodide  and  bromide  give  the 
principal  characteristic  reactions  of  iodine  and  bromine. 
Pure  substances  must  be  employed  to  furnish  the  chlorine  re- 
quired, and  the  apparatus  should  be  set  in  action  for  some  time 
before  the  commencement  of  the  experiment.  For  this  purpose 
cyanide  of  silver  alone  is  put  into  the  tube  ;  if  no  trace  of  iodide 
or  bromide  of  cyanogen  sublimes,  the  operation  may  be  pro- 
ceeded with — London  Chem.  Graz.,  June,  1857,  from  Comptes 
Mendus. 
ON  THE  CONVERSION  OF  MANNITE  AND  GLYCERINE  INTO 
TRUE  SUGAR. 
By  M.  Berthelot. 
The  analogies  existing  between  the  alcoholic  fermentation  of 
mannite  and  glycerine  and  that  of  the  true  sugars,  at  once  give 
rise  to  the  opinion  that  these  two  fermentations  might  not  really 
be  distinct ;  if  mannite  and  glycerine  furnish  alcohol,  they  pro- 
bably pass  previously  through  the  state  of  sugar. 
To  determine  this  question,  the  author  has  made  various  ex- 
periments, the  results  of  which  differed  according  to  circum- 
stances. Under  the  normal  conditions  of  the  alcoholic  fermen- 
tation of  mannite  and  glycerine,  with  the  simultaneous  influence 
