260 
Zinc  Dust. 
Am.  Jour.  Pharm. 
June,  1905. 
analyses  must  be  verified.  It  is  possible  that  in  some  cases  the 
amount  of  nitrogen  present  has  been  so  small  that  it  has  not  mate- 
rially affected  the  relation  of  carbon,  hydrogen  and  oxygen. 
Further  investigations  upon  this  subject  will  be  continued  as  time 
permits. 
ZINC  DUST. 
By  A.  B.  Stkvens. 
Before  using  zinc  dust  in  some  experiments  upon  the  gum  ob- 
tained from  Japanese  lac  I  wished  to  be  sure  that  it  was  free  from 
nitrogen ;  I  therefore  subjected  the  zinc  dust  to  the  following  tests, 
the  results  of  which  may  be  of  interest  to  those  who  frequently  use 
it  in  connection  with  organic  substances  : 
When  heated  with  potassium  hydroxide  it  formed  ammonia. 
When  heated  alone  it  also  gave  off  ammonia.  This  led  to  the  belief 
that  nitrogen  in  some  form  had  been  absorbed  from  the  atmosphere, 
and  might  be  removed  by  heat.  A  small  quantity  was  therefore 
placed  in  a  loosely  covered  crucible,  and  strongly  heated  for  half  an 
hour.  When  cold  it  was  tested  for  nitrogen  by  heating  with  potas- 
sium hydroxide.  Its  vapors  rapidly  changed  litmus  paper  from  red 
to  blue.  Upon  the  suggestion  of  Professor  Tschirch  a  sample  was 
thoroughly  washed  with  water  acidulated  with  hydrochloric  acid, 
but  this  failed  to  completely  remove  the  nitrogen. 
As  zinc  dust  is  manufactured  by  heating  zinc  oxide  with  coal,  it 
was  believed  that  part  of  the  nitrogen  might  consist  of  condensation 
products  from  the  coal.  Therefore  a  sample  was  placed  in  a  long 
tube  and  percolated  with  ether.  The  ether  when  evaporated  left  a 
yellow,  non-saponifiable  oil,  with  an  odor  and  fluorescence  similar  to 
petroleum.  The  oil,  when  heated  with  dry  potassium  hydroxide, 
gave  off  alkaline  vapors,  and  the  zinc  in  the  percolator  was  still 
found  to  contain  nitrogen.  The  greater  portion  of  the  oil  appeared 
to  be  removed  with  the  first  portion  of  ether,  but  after  continued 
percolation  the  ether  left  a  residue  upon  evaporation,  and  it  was 
evident  that  a  much  larger  amount  of  ether  was  necessary  for  com- 
plete exhaustion,  therefore  a  smaller  sample,  from  a  can  of  zinc  dust 
which  had  been  in  the  laboratory  for  more  than  ten  years,  was 
treated  with  ether  in  the  same  manner,  and  the  powder  tested  from 
time  to  time.    After  using  a  large  amount  of  ether  the  zinc  was 
