ON  COLOR  OBTAINED  FROM  COAL  TAR  PRODUCTS.  269 
the  interest  of  this  coal  tar  product  is,  that  by  the  process  we 
have  discovered,  we  can  obtain  with  it,  on  a  piece  of  calico  mor- 
danted for  madder  colors,  all  the  various  colors  and  shades 
given  by  this  valuable  root — violet,  purple,  chocolate,  pink,  and 
red.  The  only  thing  which  has  prevented  us  from  introducing 
into  the  market  the  crown  red  inodorous  paper  which  we  prepare, 
has  been,  that  it  is  as  yet  too  expensive  to  compete  with  this  ex- 
traordinary color-giving  root,  but  we  intend  pursuing  our  re- 
searches in  the  hope  of  employing  it  as  a  substitute  for  safflower 
or  cochineal,  two  coloring  matters,  the  price  of  which  is  suffi- 
ciently high  to  induce  us  to  continue  our  investigations.  We  may 
add  that  our  imitation  of  safflower  color  stands  soap  and  light, 
whilst  safflower  colors  do  not. 
I  shall  now  draw  the  attention  of  the  meeting  to  the  prepara- 
tion, dyeing,  and  printing  of  a  magnificent  crimson  color,  called 
murexide,  obtained  from  guano,  a  substance  which,  until  lately, 
has  been  entirely  imported  for  agricultural  purposes.  The  in- 
teresting application  of  this  color  to  calico  printing  has  been, 
like  many  valuable  chemical  discoveries,  progressive,  and  has 
only  been  brought  to  successful  commercial  speculation  by  suc- 
cessive discoveries,  made  by  various  persons. 
Prout  was  the  first  chemist  to  remark,  that  if  the  faeces  of 
serpents  were  heated  with  nitric  acid,  and  a  little  ammonia  added, 
a  beautiful  purple  color  was  produced.  He  named  it  purpurate 
of  ammonia.  This  substance,  when  dry,  has  the  appearance  of 
a  dark-red  powder,  soluble  in  water,  to  which  it  communicates 
a  magnificent  red  color.  This  solution  not  only  gives  a  precipi- 
tate with  metallic  salts,  but  when  evaporated  yields  beautiful 
crystals,  having  the  iridescent  appearance  of  the  wings  of  can- 
tharides. 
This  discovery  has  also  been  useful  to  medical  men,  by  en- 
abling them  to  distinguish  the  uric  acid  calculi. 
Messrs.  Liebig  and  Wohler  had  also  investigated  the  subject, 
and  succeeded  in  obtaining  from  the  uric  acid  contained  in  the 
faeces  of  serpents  this  substance,  which  they  called  murexide, 
and  a  new  class  of  organic  substances,  the  knowledge  of  which 
has  much  facilitated  the  application  of  murexide  to  dyeing  and 
printing.  Mr.  Saac  was  the  first  to  apply  the  products  of  uric 
acid  to  the  dyeing  of  fabrics  ;  his  process  consisted  in  dipping 
woollen  fabrics,  prepared  with  a  salt  of  tin,  into  a  weak  solution 
