PROPERTIES  oF  CARBO-AZOTIC  ACID. 
119 
last  disease,  not  only  the  skin  but  also  the  conjunctiva  of  the 
eyes  is  colored.  The  time  necessary  for  this  coloration  seems 
to  vary  according  to  the  patients,  from  two  to  sixteen  days,  but 
the  mean  has  been  seven  days.  The  quantity  of  carbo-azotate 
which  has  generally  produced  the  coloration  of  the  skin  has 
been  about  a  gramme.  It  disappears  in  two  or  three  days  after 
this  product  has  ceased  to  be  administered. 
We  have  sought  to  discover  the  presence  of  this  acid  in 
urines,  and  the  following  is  the  process  which  we  have  followed: — 
The  urines  were  treated  by  acetate  of  lead,  rendered  slightly 
acid  by  some  drops  of  acetic  acid.  The  abundant  white  precipi- 
tate which  is  produced  was  removed  by  filtration,  and  the  liquor 
evaporated  perfectly  to  dryness  in  an  oil  bath  kept  at  a  gentle 
heat.  The  residue  treated  by  ether  gave  an  ethereal  extract, 
which>  evaporated  to  dryness,  left  a  slight  residue,  which  residue 
dissolved  in  distilled  water,  was  divided  in  two  parts,  A  and  B. 
In  A,  was  put  boiled  silk,  which  remained  white  as  long  as  the 
patient  was  not  colored,  but  it  was  otherwise  during  the  whole 
time  of  the  artificial  jaundice.  The  depth  of  coloration  that 
the  silk  takes  augments  with  the  quantity  of  carbo-azotate  ad- 
ministered. The  portion  B  was  mixed  with  alcohol  and  ammo- 
nia, and  then  a  current  of  sulphuretted  hydrogen  was  passed 
through  it  for  half-an-hour.  When  carbo-azotic  acid  was  pre- 
sent the  solution  became  red  by  the  formation  of  picramic  acid, 
discovered  by  M.  Ge'rard.  By  these  means  we  have  been  able 
to  detect  0-01  of  carbo-azotic  acid  in  100  grammes  of  urine, 
even  when  it  has  been  kept  several  days. 
This  coloration  of  the  skin  appears  to  us  so  important  in  a 
physiological  point  of  view,  that  we  are  actively  pursuing  our 
researches  not  only  on  man  but  on  animals.  If  Braconnot,  who 
employed  carbo-azotate  of  potash,  did  not  obtain  similar  results, 
it  was  probably  due  to  the  insolubility  of  the  salt  employed,  or 
that  he  did  not  use  true  carbo-azotate  of  potash. — Chemist,  Sept. 
1856. 
