498  American  Pharmaceutical  Association.  {A™ctSber,Pi9oi.™' 
direction,  using  up  to  about  3  grammes  of  the  pyroarsenate.  In 
the  last  (tenth)  determination,  3224-85  milligrammes  of  pyroarse- 
nate yielded  2131-68  milligrammes  of  salt. 
Accordingly,  the  analytical  ratio  is 
Salt  2131-68 
==  0-66102. 
Pyroarsenate  3224-85 
But  the  chemical  formula  of  the  pyroarsenate  is  Na407As;  its 
common  atomic  weight  is,  therefore,  354. 
The  chemical  formula  of  salt  is  NaCl,  and  its  common  atomic 
weight  is  234. 
These  common  atomic  weights  are  our  fixed  standards,  namely, 
for  carbon-diamond  taken  as  12  exactly,  O  =  16,  Na  23,  CI  =  35*5, 
and  As  =  75  exactly,  without  further  decimals  whatever. 
Accordingly,  our  atomic  ratio  is 
4NaCl  214 
 z   =  — zz  =  0-66102. 
Na407/\s  354 
Since  the  analytical  ratio  agrees  exactly  with  this  our  atomic  ratio 
to  the  fifth  decimal  place,  it  proves  that  As  =  75  exactly  in  fact. 
A  simple  calculation  shows  that  if  the  atomic  weight  of  As  were 
75-01,  the  atomic  ratio  would  be  38  lower,  that  is,  0  66064. 
Since  none  of  the  observed  analytical  ratios  are  that  low,  it  is 
thereby  demonstrated  that  the  true  atomic  weight  of  arsenic  does 
not  depart  even  as  much  as  0  01  from  the  exact  number  75. 
The  mean  of  all  the  ten  determinations  made  shows  a  departure 
of  o-002  only  from  the  number  75. 
Accordingly  the  true  or  absolute  atomic  weight  of  arsenic  is  75 
exactly,  and  the  experimental  uncertainty  is  only  0-002  on  the  mean. 
In  the  same  manner  the  experimental  determinations  for  all  the 
chemical  elements  have  been  examined  in  my  work  above  specified. 
In  this  way  the  fog  that  has  for  so  many  years  rested  over  the 
atomic  weights  of  the  chemical  elements  has  been  lifted,  and  the 
use  of  false  atomic  weights  seems  to  be  no  longer  justifiable. 
The  Iodoform  Reaction  in  Analysis. 
By  Lyman  F.  Kebler,  B.  S. 
The  iodoform  reaction  has  within  recent  years  played  a  consider- 
able part  in  analytical  work,  and  we  are  generally  informed  that 
ethyl  alcohol  will  not  react  with  iodine  in  an  alkaline  solution  to 
