ADecJember^906m'}        United  States  Army  Laboratory.  565 
attacked,  with  abundant  evolution  of  nitrous  vapors  and  finally 
dissolved  and  converted  into  phosphoric  acid.  When  sufficient  phos- 
phorus had  been  converted  in  this  way,  the  excess  of  nitric  acid 
was  driven  off,  the  acid  diluted,  tested  for  arsenic,  if  necessary  freed 
from  it,  and  then  diluted  to  the  proper  strength.  Large  quantities 
of  diluted  phosphoric  acid  were  thus  made.  Or  the  capsule  was 
used  for  the  preparation  of 
Mercuric  Nitrate,  by  the  direct  action  ot  nitric  acid  upon  metallic 
mercury.  The  very  handsome  pale  yellow  mass  of  crystals  obtained 
was  then  heated  until  the  salt  was  perfectly  dry  and  more  or  less 
powdery,  and  the  heat  being  increased  carefully,  it  was  finally  con- 
verted into 
Mercuric  Oxide,  which  was  obtained  in  this  way  in  form  of  beauti- 
ful bright-red  minute  crystals,  very  superior  in  appearance  to  the 
oxide  as  ordinarily  supplied. 
Silver  Nitrate  was  another  salt  that  was  made  in  this  furnace  in 
large  quantities,  and  almost  continually  for  long  periods.  The  sil- 
ver for  this  purpose  was  supplied  by  the  U.  S.  Mint,  and  was  99.5 
per  cent,  pure,  the  0-5  per  cent,  being  copper.  Small  as  this  per- 
centage was,  in  working  up  a  hundred  ounces  of  the  metal — the 
usual  quantity — considerable  copper  nitrate  accumulated  in  the 
mother  liquid,  so  that  only  the  first  crop  of  crystals,  after  washing 
with  a  little  ice  cold  distilled  water,  could  be  utilized  without 
re-crystallization.  The  remainder,  amounting  to  one-third  or  even 
less  of  the  entire  quantity,  had  to  be  re-crystallized.  Finally,  the 
mother  liquor  was  evaporated  to  dryness,  carefully  powdered  and 
heated  until  it  became  of  a  uniform  blackish-brown  color;  then 
cooled,  dissolved  in  distilled  water,  and  the  clear,  now  colorless  fil- 
trate, boiled  with  nitric  acid  to  decompose  the  nitrite  into  which 
the  silver  salt  haci  been  partially  converted,  and  the  silver  nitrate  was 
then  crystallized  as  before,  or,  more  frequently,  was  converted  into 
Fused  Silver  Nitrate,  in  the  form  of  small  cones  ;  in  fact,  most 
of  the  silver  nitrate  was  so  converted ;  this  operation  being 
performed  on  the  general  work  table  (7")  over  a  gas  flame.  The 
silver  nitrate  was  placed  into  a  porcelain  casserole  with  cover,  care- 
fully heated  to  fusion,  and  then  as  carefully  poured  into  the  moulds 
of  silver — an  operation  which  insured  black  fingers,  and  black  stains 
on  the  face  and  wearing  apparel  of  the  operator  notwithstanding  all 
conceivable  precaution  to  avoid  them.     Personally  I  have  never 
