400 
PRUSSIAN  BLUE,  OR  HYDROCYANATE  OF  IRON. 
oxide  of  iron.  Thus,  chemically  pure  Prussian  Blue  contains 
the  elements  of  twelve  equivalents  of  water,  and  it  is  to  the 
latter  that  it  owes  its  color?  since  it  loses  it,  when  heated,  besides 
the  cyanogen  contained  being  either  lost  or  dissolved  in  its  ele- 
ments. 
In  order  to  find  out  whether  the  ferrocyanide  of  potassium 
present  in  the  so-called  hydrocyanate  was  retained  merely  as  a 
mechanical  admixture,  caused  by  the  use  of  alcohol  in  washing 
it,  I  subjected  to  examination  two  fine  specimens  of  the  officinal 
Prussian  blue,  the  one  (I.)  from  our  leading  chemical  manufac- 
turers, the  other  (II.)  from  a  prominent  German  pharmaceutist 
of  this  city. 
I.  is  a  powder  of  a  beautiful  lazur-color,  perfectly  insoluble  in 
pure  water,  and  as  completely  soluble  in  prussiate  of  potassa. 
II.  is  in  lumps,  rather  heavier  than  I.,  with  the  characteristic 
bronze  fracture  belonging  to  pure,  or  well  prepared,  Blue  ;  in 
its  qualitative  reactions  identical  with  I. 
I. 
Iron  33-2  p.  c.  of  which  32-40 
as  FeCy  14-80 
as  Fe2Q3 
18-41 
Cyanogen 
4-24  in  the  prussiate. 
Potassium 
47-20  p.  c.  of  which 
4-30  p.  c. 
II. 
p.  c.  of  which 
as  FeCy  13-35 
34-26 
as  Fe203 
p.  c. 
19-05 
2-93  p.  c. 
Taking  as  above  the  FeCy  as  ferrocyanic  acid,  we  have 
I. 
Peroxide  of  Iron         26-30  p.  c. 
Ferrocyanic  Acid       51-49  p.  c. 
Ferrocyanide  of  Potas- 
sium 11-48  p.  c. 
Water                     10  73  p.  c. 
100-00 
which  carried  out  gives 
I. 
With  Prus- 
siate of  Pot. 
Iron  31-68 
Carbon 
II. 
27-21  p.  c. 
47-44  p.  c. 
7-90  p.  c. 
17-45  p.  c. 
Nitrogen 
Water 
Prussiate  of  Potassium 
(anhydrous) 
19-83 
23-13 
15-34 
1002 
Without 
Pr.  of  Pot. 
35-21 
22-04 
25-70 
1705 
10000  10000 
100-00 
With  Prus. 
of  Pot. 
32-40 
15-81 
18-45 
26-46 
100-00 
II. 
Without 
Pr.  of  Pot. 
3479 
16-97 
19-81 
28-93 
100-00 
