258 
Substitutes  for  Chrysarobin. 
Am.  Jour.  Pliarm- 
May,  1888. 
glacial  acetic  acid,  it  is  better  to  effect  the  reductiou  by  means  of  zinc 
dust  and  ammonia,  which  have  been  previously  employed  for  similar 
purposes  by  Perger,  Bollert  and  others ;  after  boiling  for  fifteen 
minutes,  the  ammoniacal  solution  is  filtered  into  hydrochloric  acid,  and 
the  leuco-substances,  after  collecting,  washing  and  drying,  are  thus 
obtained  sufficiently  pure  for  therapeutical  use. 
The  first  experiments  were  made  with  the  reduction  product  of 
pure  flavopurpurin,  and  after  its  efficacy  was  ascertained,  the  corres- 
ponding product  of  pure  alizarin  was  prepared  and  found  to  be  equally 
efficient ;  it  does  not,  therefore,  appear  to  be  necessary  for  the  purpose 
in  view  to  keep  these  two  coloring  matters  absolutely  separate,  and 
the  subsequent  experiments  were  made  with  commercial  alizarin  and 
purpurin. 
The  reduction  product  of  alizarin  had  been  prepared  in  1881  by 
Romer,  who  named  it  desoxyalizarin ;  but  neither  this  name,  nor  the 
<;ollective  name  of  anthranols,  for  such  a  group  of  compounds,  seems 
quite  appropriate,  and  it  is  proposed  to  call  them  anthrarobins ,  in 
view  of  their  derivation  from  anthraquinol  colors,  and  of  their  chemi- 
cal and  therapeutical  relation  to  chrysarobin.  The  product  obtained 
from  commercial  alizarin  will  be  designated  as  anthrarobin,  while  those 
prepared  from  the  commercial  purpurins  will  be  distinguished  by  pre- 
jixing  the 'letter  p  or/. 
vCommercial  anthrarobin  is  a  yellowish  white  powder,  permanent  in 
the  air,  insoluble  in  water  and  dilute  acids,  but  readily  soluble  with 
a  brown  yellow  color  in  dilute  solutions  of  alkalies  and  alkaline  earths, 
the  solutions  in  contact  with  oxygen  passing  through  green  and  blue 
finally  into  alizarin  violet.  This  change  of  color  is  best  observed  by 
agitation  of  the  dilute  solution  in  a  test  tube  held  over  white  paper ; 
if  from  0.25  to  0.5  gm.  of  the  substance,  together  with  some  alkali 
solution,  be  thus  agitated  in  a  test  tube  closed  by  the  thumb,  a 
diminution  of  pressure  in  the  tube  will  be  observed. 
Anthrarobin  dissolves  with  difficulty  in  benzol  and  chloroform  ; 
but  in  glacial  acetic  acid  and  in  alcohol  it  is  much  more  soluble  than 
chrysarobin.  It  required  5  parts  of  90  per  cent,  alcohol  for  solution 
in  the  cold,  the  liquid  being  of  a  brown  yellow  color ;  hot  alcohol  dis- 
solves it  instantly.  Long  continued  boiling  causes  decomposition ; 
but  the  cold  alcoholic  solution  may,  in  a  well-corked  vial,  be  kept  for 
weeks  with  but  slight  alteration.  The  compound  is  also  soluble  in 
glycerin,  and  the  alcoholic  solution  may  be  diluted  with  glycerin  with- 
