Am.  Jour.  Pharm.  ] 
May,  1881.  | 
On  Resorcin. 
223 
which,  togetlier  with  its  explanation  is  abstracted  from  the  observa- 
tions of  Prof.  Groth,  in  his  "  Physikalische 
Krystallographie/^  p,  426.  Relation  of  axes 
a  :  b  :  G  =  0-9105  :  1  :  0-5404,  =  oo  P, 
upper  pole :  r  =  "p  oo  ,  lower  pole  :  o  =  P. 
Plane  of  optical  axis  o  P,  a  first  middle  line, 
double  refraction  — ;  for  the  iVa  line  2  V  = 
46^14^  /9  =  1-555. 
2E  =  76° W  red 
76°06^  yellow 
74°35^  blue. 
It  melts  at  104°C.,  and  boils  at  271  °C.,  but  becomes  partially  vola- 
tilized at  a  much  lower  temperature ;  it  is  very  readily  soluble  in 
water,  alcohol  and  ether,  but  is  insoluble  in  chloroform  and  carbon 
bisulphide.  Its  aqueous  solution  is  neutral  in  its  action  on  litmus, 
possesses  an  intensely  and  disagreeably  sweet  taste,  and  assumes  a  dark 
violet  color  on  the  addition  of  ferric  chloride,  which  disappears  on  the 
subsequent  addition  of  ammonia ;  chlorinated  lime  also  produces  a 
transient  violet  coloration.  Its  solution  with  ammonia  by  exposure 
to  the  air  becomes  rose-red,  then  brown,  by  evaporation  with  a  gentle 
heat  green,  finally  bark  blue,  and,  on  the  addition  of  an  acid,  again 
dark  red.  Pesorcin  reduces  nitrate  of  silver  and  an  alkaline  copper 
solution  on  boiling ;  upon  the  addition  of  bromine  water  to  its  aqueous 
.solution,  small  colorless  needles  of  tribromresorcin,  C6HBr3(OH)2,  are 
separated,  which  are  sparingly  soluble  in  cold  water,  more  readily  in 
Jiot  water  and  in  alcohol.  With  the  acid  chlorides,  acetyl,  benzoyl 
and  succinyl  chlorides,  resorcin  combines  to  form  ether-like  com- 
pounds, in  which  the  hydrogen  atoms  of  the  hydroxyl  are  replaced  by 
acetyl,  benzoyl,  or  succinyl  groups,  as  CqHJ^ — €21130)2,  etc. 
Resorcin  is  also  of  considerable  interest  from  the  fact  of  its  enter- 
ing into  the  composition  of  several  beautiful  coloring  matters,  which, 
although  yet  in  their  infancy,  promise  to  be  of  great  future  import- 
ance. When  heated  with  phtalic  anhydride  at  195°C.,  as  shown  by 
Baeyer,  the  phtalein  of  resorcin  or  fluorescein  is  produced  as  follows: 
C,Ufi^-^2C,Bfi,==C,JI,fi,-'r^iW'  From  the  solution  of  the 
melted  mass  in  alcohol  it  is  precipitated  in  white  flakes  by  water,  and 
crystallizes  from  alcohol  in  small,  dark-brown,  crystalline  crusts, 
which  dissolve  in  ammonia,  forming  a  red  solution,  and  displaying  an 
intense  green  fluorescence.    From  the  fluorescein  by  the  action  of 
