72 
COMMERCIAL  VALUE  OF  MANGANESE. 
nity  for  mercury,  or  the  powder  may  be  rendered  entirely  inert ; 
and  such  an  accident  once  befell  a  patient  of  mine,  who  nearly 
lost  her  life  before  the  cause  of  failure  of  the  medicine  in  producing 
its  proper  effects  was  discovered. — Virginia  Medical  and  Surgical 
Journal,  Nov.  1853. 
ON  A  NEW  METHOD  FOR  DETERMINING  THE  COMMERCIAL 
VALUE  OF  MANGANESE. 
By  Astlet  Paston  Price,  Ph.D.,  F.C.S., 
Chemical  Assistant  in  the  Laboratory  of  the  Government  School  of  Mines. 
It  is  well  known  that  several  methods  have  been  described  for 
determining  the  commercial  value  of  oxide  of  manganese,  that  is 
to  say  for  estimating  the  amount  of  chlorine  capable  of  being  ob- 
tained from  a  given  sample  of  manganese. 
There  are,  however,  certain  practical  inconveniences  attendant 
on  the  employment  of  many  of  these  processes,  most  of  them  de- 
manding an  amount  of  time  and  manipulation  which  is  most  de- 
sirable to  obviate.  , 
The  method  I  have  for  some  time  employed,  and  which  I  have 
found  to  give  accurate  results,  is  based  on  the  conversion  of  ar- 
senious  into  arsenic  acid  by  means  of  chlorine,  and  the  transfor- 
mation of  arsenious  into  arsenic  acid  by  the  employment  of  a  so- 
lution of  hypermanganate  of  potash. 
The  specimen  of  manganese  under  examination  is  dissolved  in 
a  normal  hydrochloric  acid  solution  of  arsenious  acid  ;  and  the  ar- 
senious acid  remaining  unchanged  into  arsenic  acid  is  determined 
by  a  standard  solution  of  hypermanganate  of  potash.  In  employ- 
ing a  solvent  containing  a  reducing  agent,  it  will  be  found  that 
the  solution  of  the  oxides  of  manganese  is  materially  facilitated, 
and  may  be  effected  at  a  low  temperature  in  a  very  short  space  of 
time. 
In  adopting  this  method,  some  difficulties  presented  them- 
selves : — 
1.  On  dissolving  arsenious  acid  in  hydrochloric  acid,  terchloride 
of  arsenic  is  given  off,  and  it  becomes  difficult  to  obtain  a  correct 
normal  solution.  This  difficulty  is  avoided  by  dissolving  the  ar- 
senious acid  in  a  solution  of  caustic  potash,  and  then  adding  the 
alkaline  solution  to  an  access  of  hydrochloric  acid. 
