VARIETIES. 
187 
considerable  quantity  of  this  coal  has  been  taken  to  San  Francisco,  and 
it  has  tended  to  reduce  the  price  of  wood  and  the  foreign  coal.  A  plentiful 
supply  of  coal  in  California  would  tend  greatly  to  facilitate  quartz-mining, 
by  enabling  the  machinery  to  be  operated  by  cheap  steam  power.  Coal 
will  also  make  California  a  great  manufacturing  State. —  Chem.  News,  Lon- 
don, Aug.  10,  1861. 
Explosion  in  making  Phosphoric  Acid. — Eisner  relates  (Chem.  tech. 
MUtheilungen,  1859-60,  s.  121)  that  some  time  since  as  a  chemist  was 
making  phosphoric  acid,  by  acting  on  phosphorus  with  nitric  acid  in  a  re- 
tort,  a  tremendous  explosion  took  place  when  the  mixture  was  heated, 
which  not  only  shattered  the  retort,  but  blew  out  all  the  windows,  and  even 
shook  the  walls  of  the  laboratory.  The  cause  of  the  explosion  he  supposes 
to  be  the  formation  of  phosphuretted  hydrogen  from  the  sudden  decompo- 
sition of  vapor  of  phosphorous  acid  into  that  gas  and  phosphoric  acid. 
Eisner  recommends  that  the  phosphorus  should  be  treated  with  nitric  acid 
in  a  large  dish,  so  that  the  vapor  of  phosphorous  acid  may  have  free  escape. 
—  Chem.  Netvs,  London,  Aug.  10,  1861. 
Emery. — The  trade  in  emery  is  not,  as  formerly,  monopolised  by  the 
Greek  Government,  which  now  levies  a  tax  of  5  drachms  per  hundred 
weight  when  exported.  Other  hard  minerals  are  sometimes  fraudulently 
substituted  for  it,  to  detect  which,  and  to  determine  the  value  of  the  emery, 
the  following  method  is  employed  in  Smyrna: — A  plate  cf  glass  of  known 
weight  is  rubbed  with  a  certain  quantity  of  the  emery  until  it  has  no 
further  effect  ;  the  lighter  the  glass  has  become,  the  better  is  the  quality 
of  the  emery.  The  emery  diggings  of  the  Government  are  on  the  island 
of  Naxos.  A  ferruginous  clay  silicate  has  lately  been  discovered  upon  the 
island  of  Skyno,  which  is  not  inferior  in  hardness  to  emery. — Chem.  News, 
London,  July  27,  1861,  from  Wittst.  V.  Schr. 
Spontaneous  Decomposition  of  Gun-cotton. — M.  Bouet  (Comptes  Ren- 
dus,  t.  liii.  p.  405)  has  remarked  that  the  decomposition  of  gun-cotton  in 
diffused  light  is  preceded  by  the  appearance  of  a  reddish  atmosphere, 
and  also  that  the  cotton  prepared  with  nitrate  of  potash  and  sulphuric- 
acid  is  sooner  and  more  violently  decomposed  than  that  prepared  with 
the  mixed  acids.  The  residue,  he  says,  is  also  different  in  the  two  cases  : 
that  of  the  first  is  something  like  burnt  sugar,  and  in  the  second  case  is 
of  a  straw  color.  In  both  cases  the  sides  of  the  bottle  were  nearly  covered 
with  small  crystals  of  oxalic  acid,  and  the  air  contained  had  an  acid  re- 
action. M.  Bouet  demonstrated  the  presence  of  carbonic  and  formic 
acids  in  the  atmosphere  of  the  bottle,  and  he  thinks  it  probable  that 
cyanogen  was  present.  No  oxide  of  nitrogen  was  discoverable.  The 
solid  residue  after  the  removal  of  the  oxalic  acid  was  white,  and  dissolved 
in  water  like  gum. 
