342 
Volumetric  Analysis, 
Am.  Jour.  Pharm. 
July, 1883. 
each  grain-measure  of  the  salt  solution)  will  give  the  exact  number  of 
grains  of  pure  silver  contained  in  one-tenth  of  a  dollar  =  37*+  grains^ 
or  371*25  grains  of  pure  silver  in  the  dollar. 
The  metric  system  of  w^eights  and  measures  is  now  used  exclusively 
(for  scientific  purposes)  in  France,  Prussia,  Austria,  Holland,  Sweden,, 
Denmark,  Belgium  and  Spain,  the  unit  of  weight  being  the  gram  (= 
15-43235  grains  troy) ;  a  gram  of  distilled  water  at  4°C.^  (39°F.)  mea- 
sures exactly  a  cubic  centimeter  or  a  "fluigram;''^  the  kilogram 
contains  1,000  grams;  the  liter  contains  1,000  fluigrams. 
The  following  apparatus  is  required  in  the  preparation  and  use  of  the 
necessary  solutions : 
1.  A  glass  flask,  which,  when  filled  to  a  mark  on  the  neck,  contains' 
one  liter. 
2.  A  graduated  cylindrical  jar,  which,  when  filled  to  o,  contains  one 
liter,  and  is  divided  into  one  hundred  equal  parts. 
3.  A  burette,  a  graduated  tube  which,  when  filled  to  o,  holds  one 
hundred  fluigrams,  and  is  divided  into  one  hundred  equal  parts. 
When  volumetric  analysis  first  came  into  use  the  test  solutions  were- 
generally  prepared  so  that  each  substance  to  be  tested  had  its  own- 
special  reagent,  and  the  strength  of  the  standard  solution  was  so  calcu- 
lated as  to  give  the  result  in  percentages  ;  consequently,  in  alkalimetry^ 
a  distinct  standard  acid  was  used  for  soda,  another  for  potash,  a  third 
for  ammonia,  and  so  on,  necessitating  a  great  variety  of  standard  solu- 
tions. 
Griffin  and  Ure  appear  to  have  been  the  first  to  suggest  the  use  of 
standard  test  solutions  based  on  the  atomic  system. 
Normal  test  solutions,  as  a  general  rule,  are  prepared  so  that  one 
liter  at  i6°C.  shall  contain  the  hydrogen  equivalent  of  the  active 
reagent  weighed  in  grams  (H  ==  i). 
Decinormal  solutions  are  made  one-tenth,  and  centinormal  solutions^ 
one-hundredth,  of  this  strength. 
In  the  case  of  univalent  substances,  such  as  silver,  iodine,  hydro- 
chloric  acid,  sodium,  etc.,  the  equivalent  and  the  atomic  (or  in  the  case 
of  salts,  molecular)  weights  are  identical  ;  thus  a  normal  solution  of 
^  It  is  customary  to  make  the  measurements  with  metrical  apparatus  at  16^0. 
(about  60OF.) 
2  This  name  was  suggested  by  the  author  in  a  paper  published  in  the  "Medical 
and  Surgical  Reporter,"  Feb.  24,  1877,  P*  iJi* 
