Am.  Jour.  Pharm.  \ 
April,  19 1 7. 
Assay  Processes. 
173 
the  oil.  The  acid  number  for  resins  implies  the  number  of  Mgs, 
KOH  required  to  neutralize  one  gram  of  the  resin. 
One  compound  of  the  U.  S.  P.,  liquid  petrolatum,  contains  a 
viscosity  test.  It  is  conducted  by  placing  a  mark  at  2  Cm.  below  the 
bulb  of  a  50  mil  pipette,  filling  with  distilled  water  to  the  upper 
level,  and  noting  the  time  in  seconds  required  for  the  level  of  the 
water  to  reach  the  lower  mark.  The  liquid  to  be  tested,  is  then 
drawn  to  the  upper  mark  of  the  pipette,  and  the  time  in  seconds  it 
requires  to  reach  the  lower  level,  divided  by  the  number  of  seconds 
taken  by  the  water,  indicates  its  viscosity. 
Under  each  drug  is  given  the  percentage  of  the  limit  of  ash  it 
should  contain. 
Some  of  the  zinc  and  mercury  compounds  are  tested  electro- 
lytically. 
Amylolytic  and  proteolytic  methods  are  also  included  among  the 
U.  S.  P.  assay  methods;  the  former  for  pancreatin,  diastase  and 
malt ;  the  latter  for  pepsin. 
In  addition  to  the  chemical  methods  of  assay,  several  of  the 
drugs  are  directed  to  be  assayed  biologically :  aconite,  digitalis,  stro- 
phantus and  squills.  The  biological  method  is  also  used  in  con- 
nection with  biological  substances  now  included  in  the  Pharma- 
copoeia :  suprarenal  gland,  dried  hypophysis,  serums,  etc. 
ALKALOID AL  ASSAYS. 
The  active  constituents  of  a  large  number  of  the  vegetable  drugs 
reside  in  alkaloids.  Time  will  not  permit  of  detailing  these  methods. 
With  but  one  or  two  exceptions  the  alkaloids  are  determined  vol- 
umetrically.  The  drug  is  macerated  with  a  mixture  of  one  volume 
of  chloroform  and  two  of  ether.  After  standing  a  short  time  am- 
monia water  is  added,  and  shaken  vigorously  every  ten  minutes  for 
two  hours.  Some  water  is  added,  and  the  whole  allowed  to  settle. 
The  liquid  is  decanted,  and  an  aliquot  part  filtered  through  cotton 
into  a  separator.  The  alkaloids  are  extracted  by  shaking  out  with 
weak  sulphuric  acid.  The  acid  washings  are  made  alkaline  with 
ammonia  water  and  are  extracted  by  repeated  shakings  with  chloro- 
form. The  chloroform  solution  is  evaporated  and  dissolved  in  an 
excess  of  n/10  sulphuric  acid,  and  the  excess  of  acid  used  is  ti- 
trated with  w/50  alkali,  cochineal  being  used  as  an  indicator.  From 
the  number  of  mils  of  acid  consumed,  the  per  cent,  of  alkali  is  de- 
termined by  multiplying  by  its  coefficient,  and  dividing  by  the 
