Am'jJu°ne;iP9S5arm-}  ZijlC  Dust.  26 1 
practically  free  from  nitrogen,  yet  by  taking  a  large  amount  of  the 
zinc  and  heating  with  potassium  hydroxide  in  a  tube  partially  closed 
at  the  top  so  that  all  of  the  vapors  came  in  contact  with  the  litmus 
paper,  the  color  was  slightly  changed,  thus  showing  a  mere  trace  of 
nitrogen.  This  sample  was  then  allowed  to  stand  in  an  open  flask 
for  a  few  days  when  it  gave  a  decided  ammonia  reaction,  thus  show- 
ing that  zinc  dust  rapidly  absorbs  nitrogen  from  the  air. 
The  fact  that  only  a  portion  of  the  nitrogen  in  zinc  dust  is  removed 
by  heat  indicates  that  the  nitrogen  is  present  in  more  than  one  form. 
This  theory  is  also  supported  by  the  following  experiments : 
A  fresh  sample  of  zinc  dust  was  washed  with  water,  the  washings 
giving  a  decided  ammonia  test.  The  washing  was  continued  as  long 
as  traces  of  nitrogen  could  be  detected  in  the  washings.  It  was 
then  treated  in  the  same  manner  with  very  dilute  hydrochloric  acid. 
By  adding  potassium  hydroxide  in  excess  to  the  acid  solution  and 
allowing  to  stand  a  few  minutes  until  the  precipitate  settled,  decant- 
ing the  clear  solution  and  boiling,  the  vapors  gave  the  odor  of 
ammonia  and  rapidly  changed  litmus  from  red  to  blue.  Washing 
with  acid  was  continued  until  the  washings  no  longer  gave  a  test  for 
nitrogen.  The  zinc  was  then  washed  with  water  until  free  from  acid, 
and  rapidly  dried  in  a  drying  oven,  and  at  once  extracted  with  ether, 
the  ether  evaporated  and  tested  for  nitrogen  as  above.  Nitrogen 
was  found  to  be  present,  though  not  in  as  large  amounts  as  in  the 
oil  from  the  first  sample  examined,  which  was,  however,  directly 
treated  with  ether. 
Three  samples  were  examined :  one  from  a  large  closely  covered  can 
which  has  been  in  use  in  the  laboratory  as  above  stated  ;  another 
from  a  glass  bottle  which  has  been  in  the  museum  about  fifteen 
years,  and  a  third  which  was  ordered  by  Professor  Oesterle  for  these 
experiments.  Practically  the  only  difference  found  in  the  three 
samples  was  that  the  oil  from  the  fresh  sample  was  decidedly  yellow, 
while  that  from  the  laboratory  sample  was  somewhat  lighter,  and 
that  from  the  museum  sample  was  colorless. 
Dr.  Victor  Steger  ("  Metalldampfe  in  Zinkhiitten,"  Chemischer 
und  Chemischtechnischer  Vortrage)  gives  the  results  of  several 
analyses  of  zinc  dust,  some  of  which  contain  considerable  insoluble 
residue  consisting  principally  of  carbon.  To  determine  to  what 
extent  this  was  present,  a  large  amount  of  zinc  dust  was  treated  with 
hydrochloric  acid.    At  first  the  reaction  was  rapid,  but  after  a  time 
