VARIETIES. 
475 
addition  of  a  slight  yellowish  green  tint.  Every  drachm  and  a  half  con- 
tains ten  grains  of  sulphate  of  iron,  which,  with  a  complement  of  bicar- 
bonate of  soda,  is  certain  to  produce,  in  a  state  of  solution,  four  grains  of 
nascent  protocarbonate  of  iron. — London  Pharm.  Journ.  Aug.,  1861. 
New  Test  for  Diabetes. — This  test  consists  in  the  conversion  of  the  sac- 
charine element  of  diabetic  urine  into  caramel  by  heat. 
The  following  is  the  mode  of  applying  it: — 
Upon  a  clean  slip  of  tinned  iron  place  one  or  two  drops  of  the  suspected 
material,  and  hold  it  over  a  spirit  lamp  ;  the  fluid  will  speedily  evaporate, 
leaving,  if  the  process  be  arrested  at  that  point,  scarcely  a  trace  upon  the 
metallic  surface.  Continue  the  application  of  heat ;  in  a  few  moments 
after  the  desiccation  is  complete,  a  spot  of  an  inch  or  so  in  diameter,  over 
which  the  drops  spread  with  the  first  ebullition,  will  gradually  assume  a 
rich  reddish-brown  color,  with  a  brilliant  lustre,  as  if  coated  with  a  film  of 
Japan  lacquer.  A  solution  of  sugar,  not  diabetic,  exhibits  almost  exactly 
the  same  reaction. — London  Pliarin.  Journ.  Aug.  1861. 
Manufacture  of  Pure  Phosphoric  Acid. — Dr.  J.  Neustadtl  publishes  (Din- 
gler's  Polytech.  Journal,  Bd.  clix,  s.  442)  an  «'  improved  method  of  making 
pure  phosphoric  acid  on  the  large  scale.^^  The  process  involves  the  pre- 
paration of  phosphate  of  soda  from  bone  ash,  the  formation  of  phosphate 
of  baryta  from  this,  and  the  subsequent  decomposition  of  the  last  by  sul- 
phuric acid.  In  the  first  place,  one  part  of  finely  powdered  bone  ash  is 
mixed  with  four  parts  of  water  and  one  part  hydrochloric  acid.  After 
standing  six  hours,  the  clear  liquid  is  poured  ofi",  and  to  it  is  added  aboiling 
solution  of  sulphate  of  soda.  The  sulphate  of  lime  is  allowed  to  deposit, 
tho  liquor  is  poured  ofi",  and  the  precipitate  washed  and  pressed.  The 
liquor  decanted,  which  contains  acid  phosphate  of  soda,  chloride  of  sodium, 
and  some  sulphate  of  lime,  is  now  boiled  with  carbonate  of  soda  and  ren- 
dered neutral,  and  then  filtered  from  the  precipitated  carbonate  of  lime. 
We  have  now  a  neutral  solution  of  phosphate  of  soda,  and  chloride  of  sodi- 
um, to  which  is  added  just  enough  of  a  hot  solution  of  chloride  of  barium 
to  precipitate  the  phosphoric  acid  in  the  form  of  phosphate  of  baryta. 
Twice  the  weight  of  the  bone-ash  operated  on,  the  author  says,  is  the 
quantity  of  chloride  of  barium  required.  After  washing,  the  phosphate  of 
baryta  (prepared  from  one  part  of  bone-ash)  is  mixed  with  one  part  of 
sulphuric  acid  diluted  with  three  parts  of  water,  and  stirred  occasionally 
for  two  or  three  days,  until  no  sulphuric  acid  is  found  in  the  liquor,  which 
is  then  strong  and  pure  phosphoric  acid. —  Chem,  News,  London. 
