ON  SOME  CONSTITUENTS  OF  RHUBARB. 
445 
phenomena  being  accompanied  by  the  disappearance  of  the  floc- 
culent  precipitate.  The  solution,  however,  recovers  its  original 
purple  color  when  exposed  in  a  shallow  vessel  to  the  air  for  a 
few  minutes,  and  the  flocculent  precipitate  is  again  formed. 
Hydrate  of  potash,  at  its  fusion  point,  does  not  alter  chryso- 
phane at  first ;  but  if  the  temperature  be  raised,  or  the  action 
continued  for  some  time,  it  first  becomes  blue,  and  is  then  de- 
composed, at  the  same  time  an  odor  resembling  that  of  caprylic 
alcohol  is  emitted.  Potassium  alcohol  apparently  does  not  destroy 
chrysophane  ;  it  gives  rise  to  a  purple  compound  and  formation 
of  alcohol. 
Neither  chlorine,  bromine,  nor  nitric  acid,  destroys  the  yellow 
color  of  chrysophane  ;  but  they  undoubtedly  alter  its  composi- 
tion. Nitromuriatic  acid,  when  boiled  for  some  time  with  chryso- 
phane, forms  a  liquid  body  which  does  not  become  crystalline 
on  cooling ;  but  it  still  retains  the  property  of  striking  a  red 
color  with  caustic  alkalies.  A  mixture  of  hydrochloric  acid  and 
chlorate  of  potash  behaves  in  a  somewhat  similar  manner.  If 
chrysophane  be  dissolved  in  strong  sulphuric  acid,  and  peroxide 
of  manganese  be  then  added,  the  red  color  disappears,  in  con- 
sequence of  the  destruction  of  the  chrysophane. 
0.1426  gramme  of  chrysophane  gave  on  combustion  : — 
0.3595  gramme  of  carbonic  acid  =  68.76  per  cent,  carbon. 
0.0545  gramme  of  water  =  4.25     »  hydrogen. 
If  these  numbers  be  compared  with  those  obtained  by  Roch- 
leder  and  Heldt,  who  analyzed  the  substance  obtained  from  the 
lichen  Parmelia  parietina,  and  by  Schlossberger  and  Dopping, 
who  analyzed  the  chrysophane  of  rhubarb,  there  will  be  found  a 
perfect  accordance  in  the  results,  as  will  be  seen  from  the  fol- 
lowing table  : — 
Rochleder  and  Heldt.       Schlossberger       De  la  Rue 
i.  n.  and  Dopping.       and  MiUIer. 
Carbon,  68.45  68.65  68.69  68.76 
Hydrogen,   4.56        4.59  4.24  4.25 
Oxygen,     26.99      26.76         27.07  27.09 
Before  concluding  these  observations  respecting  chrysophane. 
we  are  desirous  of  calling  attention  to  the  remarkable  resem- 
blance existing  between  the  properties  of  that  body  and  pipitza- 
