^'"A{ig'I'"i^75™*}  Action  of  Sulphuric  Acid  upon  certain  Salts.  369 
lated  yield.  He  recommended  the  process  as  easy  of  execution.  The 
most  complete  description  has  been  given  by  Pourcel.*  According  to 
him,  Tessi^  du  Motay  employs  for  retorts  cast-iron  ellipsoids,  which  lie 
horizontally  side  by  side  and  are  divided  by  a  grate  into  tv70  equal  por- 
tions parallel  vv^ith  their  axis.  Upon  the  grate  are  spread  in  each  retort 
350  kilos,  of  manganate  of  soda,  or  the  corresponding  reduced  mixture 
of  soda  and  manganese,  in  such  a  manner  that  its  thickness  amounts  to 
o*6  of  a  metre,  and  the  empty  space  above  and  below^  the  mass  is  as 
small  as  possible.  In  Comines,  vi^here  five  such  retorts  are  in  action, 
the  daily  production  amounted  to  140  cubic  metres  of  oxygen,  w^ith  an 
expenditure  of  450  kilos,  of  coal  for  heating  the  retorts  and  150  kilos, 
for  the  steam-engine. — Chem.  News^  May  and  June. 
(To  be  continued.) 
ACTION  OF  STRONG  SULPHURIC  ACID,  SP.  GR  1-843,  UPON 
CERTAIN  SALTS. 
BY  THOMAS  GARSIDE,  F.  C.  S. 
When  14  parts  of  baric  sulphate  were  added  to  100  parts  of  sulphu- 
ric acid,  and  the  mixture  rubbed  against  the  sides  of  the  test-tube  with 
a  glass  rod,  a  nearly  clear  solution  was  effected  after  some  time. 
When  the  temperature  of  this  was  raised  to  100°  C,  needle-shaped 
crystals  were  produced  in  large  quantity;  at  160°  to  180°  these 
entirely  disappeared,  but  others  of  prismatic  shape  began  to  form,  and 
increased  in  quantity  as  the  temperatue  approached  the  boiling-point  of 
the  acid.  At  a  boiling  heat  100  parts  of  the  acid  retained  between  8*5 
and  9  parts  of  the  salt  in  solution.  When  the  mixture  was  cold,  the 
whole  of  the  salt  re-dissolved  upon  stirring,  and  a  perfectly  clear  solu- 
tion was  obtained. 
The  needle-shaped  crystals  which  formed  at  100°  did  not  re-dissolve 
in  the  cold  acid. 
Strontic  sulphate  was  soluble  to  the  extent  of  14  parts  in  100  parts  of 
acid  at  70°  C.  If  the  temperature  was  lowered  from  this  point,  tab- 
ular rhombic  crystals  were  produced  ;  if  it  were  raised,  others  having 
the  form  apparently  of  cube  and  octahedron  were  deposited. 
Anhydrous  calcic  sulphate  added  to  sulphuric  acid  in  the  proportion  of 
8*25  parts  to  100,  was  converted  at  15°  C.  into  needle-shaped  crystals. 
These  disappeared  and  complete  solution  was  effected  at  about  70°  C. 
*  Pourcel,  "  Memoires  de  la  Societe  des  Ingenieurs  Civilis,"  P  1873. 
24 
