274 
Varieties. 
f  Am.  Jour.  Phai  m. 
t       June,  1875. 
nltering  paper  ;  these  scaJes  are  now  dissolved  in  twenty  times  their 
weight  of  distilled  water,  and  heated  to  200°  F.;  when  the  nitrate  of 
urea  is  all  dissolved,  animal  charcoal  (four  times  as  much  as  the  weight 
of  nitrate  of  urea  used)  is  added,  the  whole  brought  up  to  a  boil,  and 
kept  boiling  for  three  minutes,  filtered,  the  filtrate  evaporated  to  one- 
eighth  its  bulk,  and  allowed  to  crystallize  (if  the  crystals  are  not  suffi- 
ciently white  the  operation  must  be  repeated)  ;  the  white  crystals  of 
nitrate  of  urea,  dissolved  in  twenty  times  their  weight  of  water,  are 
mixed  with  pure  carbonate  of  barium  (  parts  carbonate  of  barium 
to  parts  nitrate  of  urea)  ;  the  mixture  disengages  carbonic  acid  gas, 
nitrate  of  barium  and  free  urea  being  formed.  The  whole  mass  is 
evaporated  to  dryness  o\  er  a  water-bath,  the  residue  treated  with  twenty 
times  its  weight  ot  water,  and  again  evaporated  to  dryness  ;  this  residue 
heated  to  boiling  with  95  per  cent,  alcohol,  filtered,  the  filtrate  evapo- 
rated to  one-fourth  its  volume  and  allowed  to  crystallize  ;  the  crystals 
dried  over  sulphuric  acid  are  perfectly  pure,  and  should  be  kept  in  a 
well-stoppered  bottle,  as  they  readily  deliquesce.  The  advantages  of 
the  above  are,  ist.  Spontaneous  evaporation,  whereby  the  urine  is  not 
at  all  decomposed.  2d.  Direct  addition  of  nitric  acid,  whereby  alka- 
line fermentation  and  destruction  of  urea  are  pievented.  3d.  Purifica- 
tion of  the  nitrate  of  urea,  whereby  a  pure  urea  is  obtained.- — American 
Chemist.^  April ^  1875. 
Summer  School,  Jefferson  Medical  College, 
Philadelphia,  March  1.,  1875. 
VARIETIES. 
Estimation  of  Quinia  in  Cinchona  Barks. — Perret  uses  soluble  glass  (silicate 
of  sodium )  in  the  following  manner  :  Heat  10  grms.  bark  for  ten  minutes  with  50  grms. 
alcohol  and  5  grms.  silicate  of  sodium  (40°  B.),  filter,  repeat  the  heating  twice,  first 
with  30  grms,  alcohol  and  2.5  grm.  silicate  of  sodium,  then  with  20  grms.  alcohol. 
Evaporate  the  filtrates  to  syrupy  consistence,  treat  the  mass  with  first  30  grms.  then 
with  20  grms.  and  at  last  with  10  grms.  ether.  Evaporate  the  ethereal  filtrates,  acid- 
ulate with  sulphuric  acid,  and  estimate  quinia  as  sulphate.  This  quinia  contains 
only  traces  of  quinidia  and  cinchonidia. — Ber.  d.  d.  chem.  Ges,  1874,  p.  735. 
Solubility  of  Sulphate  of  Calcium.  By  Erlenmeyer. — Sulphate  of  calcium 
dissolves  in  water  in  much  larger  quantities  (than  supposed)  when  it  has  previously 
been  heated  to  120'' — 130°  C.  (248 — 266°  F.),  until  it  no  longer  loses  in  weight. 
If  this  dehydrated  calcium  sulphate  be  shaken  with  50  parts  of  distilled  water  for 
ten  minutes,  and  filtered,  it  will  soon  commence  to  deposit  crystals,  which  increase 
