A,11'jJuiUvr;iS8arra'}      Volatility  of  Some  of  the  Newer  Remedies.  337 
tained  by  examining  the  tubes  in  strong  daylight  or  by  artificial 
light  and  noting  the  refraction  of  light  caused  by  the  minute  crys- 
tals. Exalgin,  at  30°-40°  C,  showed  a  sublimate  after  twenty-four 
hours'  heating,  and  at  4°a-5°°  C.  in  from  nine  to  twelve  hours' 
heating.  Acetanilid,  at  30°-40°  C,  showed  no  signs  of  a  sublimate 
after  forty-eight  hours,  and  at  40°-50°  C.  but  a  faint  sublimate  after 
forty-eight  hours.  Methacetin  and  phenacetin  yielded  no  sublimate 
until  heated  for  some  time  to  90°-ioo°  C.  Lactophenin,  under  the 
same  conditions,  gave  no  positive  evidence  of  volatility. 
Prolonged  heating  was  necessary  in  these  experiments,  owing  to 
the  relatively  small  surface  exposed  ;  the  recent  experiments  were 
made  by  heating  the  substances  placed  in  watch-crystals  in  a  water- 
oven,  the  opening  in  which  for  the  escape  of  volatile  products  was 
closed  by  a  cork  carrying  a  glass  tube  about  6  inches  long  and  y2 
inch  in  diameter,  through  which  the  thermometer  was  introduced ; 
this  tube  enabled  the  detection  of  sublimates.  One-half  gramme 
each  of  exalgin,  acetanilid,  methacetin,  phenacetin  and  lactophenin 
were  placed  in  weighed  watch-crystals  2^<  inches  in  diameter,  and 
heated  in  the  water-oven  for  the  specified  time  ;  the  temperatures 
represent  respectively  initial  and  final  readings  for  the  experiment 
when  two  are  stated  ;  after  cooling  in  a  dessicator  and  weighing,  the 
weight  of  the  watch-crystal  was  subtracted,  giving  the  weight  of 
the  powder  at  the  end  of  each  experiment ;  the  differenc  between 
two  successive  weighings  will  give  the  loss  sustained  in  heating  for 
the  stated  period  and  at  the  stated  temperatures.  It  will  be  noticed 
that  in  some  cases  there  is  an  increase  in  weight  ;  this  is  probably 
due  to  absorption  of  some  of  the  more  volatile  substance  by  the 
less  volatile ;  a  slight  difference  may  also  be  caused  by  allowing 
more  or  less  time  to  elapse  between  the  placing  of  the  watch-crys- 
tals with  contents  in  the  dessicators-  and  the  weighing. 
The  results  are  tabulated  in  the  order  in  which  the  experiments 
were  made ;  in  the  last  four  only  a  single  substance  was  heated  so 
as  to  recognize  the  formation  of  sublimates  ;  the  loss  of  a  half-milli- 
gramme gave  abundant  evidence  as  a  sublimate.  From  the  table  it 
will  be  seen  that  exalgin,  acetanilid,  methacetin  and  phenacetin  are 
volatile  in  the  order  given,  which  corresponds  also  to  the  order  of 
their  melting  point ;  the  decided  difference  between  these  four  and 
lactophenin  is  no  doubt  chiefly  due  to  the  fact  that  the  first  four  con- 
tain the  acetyl  group,  while  lactophenin  contains  the  lactyl  group. 
