VARIETIES.  183 
ing  in  the  air  this  mass  was  found  to  have  the  composition  IIO30-7,MgO 
69-3,  showing  it  to  be  a  simple  hydrate  of  magnesia.    With  similar  mag- 
nesia the  author  took  casts  of  medals,  as  with  plaster  of  Paris,  and  on 
placing  the  casts  in  water  found  them  to  assume  the  appearance  of  marble. 
M.  Balard's  magnesia — that  is,  the  magnesia  prepared  by  calcining  the 
chloride  obtained  by  the  treatment  of  sea-water, — calcined  at  a  red-beat 
shows  astonishing  hydraulic  qualities.     Calcined  at  a  white-heat  for  hours 
its  hydraulic  qualities  are  in  part  destroyed.     A  mixture  of  chalk  or  mar- 
ble and  magnesia  forms  with  water  a  plastic  mass,  which  after  remaining 
some  time  in  water  becomes  extremely  hard.    With  a  mixture  of  equal 
parts  of  this  magnesia  and  powdered  marble,  the  author  hopes  to  make 
busts  which  by  hydration  will  be  converted  into  artificial  marble.     A  mix- 
ture of  plaster  of  Paris  and  magnesia  he  finds  to  break  up  under  water 
The  next  experiments  are  of  great  importance.     The  author  finds  that  a 
dolomite  rich  in  magnesia  when  calcined  below  a  dull  red-heat  and  powd- 
ered and  made  into  a  paste,  forms  under  water  a  stone  of  extraordinary 
hardness.    M.  Deville  exhibited  to  the  Academy  specimens  he  had  made 
with  the  dolomite  used  by  Messrs.  Bell,  of  Newcastle,  for  making  Epsom 
salts  by  Mr.  Pattin son's  process.     When  the  dolomite  is  strongly  iguited 
and  some  quick-lime  produced,  the  mass  does  not  set  so  well,  crystals  of 
arragonite  separating  in  thin  veins.    When  dolomite  is  heated  to  bright 
redness,  and  all  the  chalk  converted  into  quick-lime,  the  paste  formed  with 
it  breaks  up  in  water.    All  the  experiments,  M.  Deville  states,  show  that 
the  magnesia  is  the  binding  material,  which  in  becoming  hydrated  holds 
together  the  particles  of  chalk  or  marble  to  form  a  compact  homogeneous 
stone.    He  has  exposed  some  of  the  stones  to  the  action  of  the  sea  in  the 
port  of  Boulogne,  and  they  at  preseut  remain  unaltered.    The  facts  con- 
tained in  this  note  proved  the  perfect  hydraulicity  of  pure  magnesia  by  the 
formation  of  a  definite  hydrate. 
The  experiments  with  dolomite  are  of  the  most  importance  to  us,  and  no 
doubt  some  of  our  readers  will  follow  up  the  experiments  made  by  the  ac- 
complished author  of  this  note. — London  Chem.  News,  Dec.  15,  1865. 
Chloroform  for  Removing  Stains  of  Dry  Paint.  By  Thomas  B.  Groves, 
F.C.S. — An  accident,  involving  the  loss  of  several  ounces  of  chloroform  at 
a  time  when  in  consequence  of  a  sudden  and  unprecedented  demand,  it  was 
peculiar^  valuable,  introduced  me  to  the  knowledge  of  a  fact  I  was  pre- 
viously unaware  of,  viz.,  that  chloroform  is  capable  of  exerting  a  powerful 
solvent  action  on  dry  white-lead  paint.  . 
The  accident  happened  in  this  way.  The  four  ounce  measure  I  was 
using  had  been  broken,  and  afterwards  carefully  mended  with  white  lead, 
several  months  being  allowed  for  it  t )  become  thoroughly  hard.  In  that 
state  it  was,  as  I  imagined,  capable  of  resisting  for  at  least  a  short  time, 
the  action  of  any  of  the  more  powerful  solvents  to  be  found  in  a  chemist's 
shop.    On  pouring  chloroform  into  it,  however,  I  was  at  once  undeceived, 
