586 
Nitrated  Silk. 
Am.  Jour.  Pharm. 
Nov.,  1892. 
obtained  by  treatment  with  permanganate  contained  about  30  per 
cent,  of  aromatic  hydrocarbons. 
On  nitration  of  the  oil,  a  certain  quantity  was  always  unattacked  ; 
this  consists  of  naphthenes,  and  the  proportion  increases  as  the 
boiling  point  of  the  oil  rises,  and  varies  from  14-5  per  cent,  in  the 
fraction  boiling  at  90-IOO0  to  33-3  per  cent,  in  the  part  boiling  at 
3000. 
No  evidence  of  the  presence  of  terpenes  in  the  oil  could  be 
obtained  on  treating  the  oil  by  Wallach's  methods.  Indene  and 
cumarone,  also,  could  not  be  detected.  The  fraction  boiling  at 
180-2400  was  found  by  treatment  with  picric  acid  to  contain  4-5 
per  cent,  of  naphthalene. 
NITRATED  SILK.1 
By  L.  Vignon  and  P.  Sisley. 
When  silk  is  immersed  in  ordinary  nitric  acid  (sp.  gr.  I "133)  at 
450  for .  one  minute,  and  is  subsequently  washed  in  water,  it  is 
colored  intensely  yellow,  and  the  color  is  unaffected  by  exposure  to 
air  and  light,  whilst  it  is  deepened  by  the  action  of  dilute  alkali 
solutions.  Nitric  acid  free  from  nitrous  compounds  does  not  cause 
this  coloration,  which  is  found  to  vary  in  intensity  directly  with  the 
amount  of  nitrous  compounds  present,  and  with  the  temperature 
and  specific  gravity  of  the  acid  used.  The  deepening  of  color  by 
alkaline  solutions  is  independent  of  their  causticity,  whilst  the  silk 
increases  in  weight  and  takes  up  a  certain  amount  of  the  base. 
Silk  treated  with  a  mixture  of  hydrochloric  acid  and  sodium 
nitrite  is  colored  pale  yellow ;  the  color  is  rapidly  browned  on 
exposure  to  air  and  light,  or  by  the  action  of  boiling  water  or 
alcohol,  whilst  cold  alkaline  solutions  turn  it  reddish-brown.  Silk 
which  has  been  subjected  to  the  action  of  nitrous  acid,  or  of  nitric 
oxide,  in  an  atmosphere  of  carbonic  anhydride,  and  subsequently 
well  washed,  is  colorless,  but  is  colored  a  stable  yellow  by  nitric 
acid.  Nitric  peroxide  colors  silk  yellow  at  once.  Silk  heated  with 
nitrous  acid,  and  then  oxidized  with  potassium  permanganate  and 
hydrochloric  acid,  is  colored  exactly  as  by  nitric  acid  (impure),  from 
which  it  seems  that  the  yellow  coloration  is  dependent  on  the  action 
of  nitrous  compounds,  and  subsequently  of  an  oxidizing  agent. 
1  Bull.  Soc.  Chim.  [3],  6,  898;  Jom\  Chem.  Soc,  September,  1892,  p.  nil. 
