264  FORMATION  OF  ACETYLENE  IN  INCOMPLETE  COMBUSTIONS. 
ascertained  by  observing  the  traces  of  acetylene  it  contains  in 
its  normal  state. 
I  have,  on  the  contrary,  obtained  no  result,  either  with  a  mix- 
ture of  oxide  of  carbon  and  hydrogen  or  with  hydrogen  charged 
with  pure  carbon  dust,  or  directed  in  a  jet  on  a  stick  of  retort 
coke. 
Not  only  is  acetylene  formed  during  combustion,  in  a  half 
covered  vessel  of  hydrocarbonated  compounds,  but  it  is  produced 
and  discharged  into  the  atmosphere  whenever  an  organic  com- 
pound burns  in  contact  with  the  air  with  formation  of  lamp-black. 
This  may  be  seen  by  placing  the  mouth  of  a  tube  over  the  flame, 
far  enough  off  not  to  interfere  with  the  combustion,  and  by  draw- 
ing away  the  gases  produced  by  the  aid  of  a  slow  flow  of  water  (one 
or  two  litres  per  minute).  A  dry,  empty  flask,  of  about  a  litre,  is 
thus  filled  by  displacement  with  the  gases  of  the  combustion. 
After  several  minutes,  put  into  the  flask  a  few  drops  of  ammonia- 
cal  cuprous  chloride,  and  the  characteristic  precipitate  will  be  pro- 
duced, though  much  less  abundantly  than  in  a  half  covered  vessel. 
I  have  especially  obtained  this  result  by  burning  the  following 
bodies  in  a  small  capsule  : — Ordinary  ether  ;  benzole,  C12H6;  oil 
of  turpentine  C20H16;  petroleum;  vegetable  oil;  stearic  acid, 
naphthaline,  C^Hg. 
The  results  given  by  benzole  and  naphthaline  merit  attention 
from  the  fact  that  I  have  hitherto  failed  to  transform  these  car- 
bides into  acetylene  by  heat  alone.  This  is  another  proof  of  the 
extreme  stability  of  acetylene,  particularly  when  mixed  with 
a  certain  portion*  of  foreign  gases. 
The  same  observations  are  applicable  to  the  combustion  of  coal 
gas.  The  gases  discharged  into  the  air,  whether  by  the  flame  of 
a  burner  known  as  the  bat's-wing,  or  by  the  smoky  flame  of  one 
of  Bunsen's  burners,  contain  a  notable  proportion  of  acteylene. 
These  observations  will  explain  the  odor  observable  in  rooms 
where  gas  is  burnt.  However,  acetylene  in  the  air  exercises,  by 
itself,  no  specially  pernicious  physiological  action  ;  for  I  have 
ascertained,  by  an  experiment  in  which  M.  Arm.  Moreau  was 
kind  enough  to  join  me,  that  its  poisonous  action  is  not  more 
marked  than  that  of  ordinary  carbides  of  hydrogen.  But  its 
presence  is  an  evidence  of  incomplete  combustion ;  such  a  com- 
