76 
Seidlitz  Powders. 
I  Am.  Jour.  Pharnu 
1    February,  1902. 
a  portion  of  Seidlitz  mixture,  all  made  from  the  CP.  salts,  were 
exposed  under  ordinary  conditions,  that  is,  in  a  room  ranging  from 
18°  to  22°  C„  and  their  weight  taken  every  two  or  three  days  during; 
the  course  of  four  weeks.  They  were  then  placed  in  a  room 
decidedly  warmer  than  the  average,  ranging  from  280  to  330  C, 
and  the  weights  taken  as  in  the  former  case.  In  both  cases  it  was 
found  that  the  condition  of  the  weather  had  a  good  deal  to  do  with 
the  weights. 
The  characteristic  results  obtained  by  these  experiments  are  best 
shown  by  a  table,  as  follows  : 
Temperature  i8°  to  220  C. 
Temperature  280  to  330  C. 

Substance 
Taken  and 
Weight  in 
Grammes. 
Weather  and 
Date. 
Loss  in 
Grammes. 
Per  Cent, 
of  Loss. 
Weather  and 
Date. 
Loss  in 
Grammes. 
Per  Cent, 
of  Loss. 
Nov.  3,  1900,  Started  Experiment. 
1901. 
Nov.  27th  wet. 
•002 
•025 
Jan.  3d  wet. 
•009 
•112 
Rochelle  salt, 
8,000. 
Dec.  9th  dry. 
•007 
•087 
"     10th  dry. 
'0115 
'143 
"    15th  wet. 
•000 
"    12th  wet. 
•008 
100 
Sodium 
Bicarbonate, 
2-6oo 
Nov.  27th  wet. 
Dec.  9th  dry. 
"    15th  wet. 
•004 
•009 
•0025 
■is 
'34 
•09 
Jan.  3d  wet. 
"     10th  dry. 
"    12th  wet. 
•004 
•012 
•005 
15 
•46 
•19 
Seidlitz 
Mixture, 
10-333 
Nov.  3d  wet. 
Dec.  9th  dry. 
"    15th  wet. 
■065 
•099 
•092 
•63 
•95 
•89 
Jan.   3d  wet. 
"     10th  dry. 
"    12th  wet. 
•104 
•i45 
•127 
i*oo6 
1 '4°3 
1*229 
Rochelle  salt  contains  25.52  per  cent,  water  of  crystallization. 
To  determine  the  loss  sustained  by  heating  to  various  temperatures 
a  portion  was  heated  in  an  air  bath : 
At  ioo°  the  loss  was  23-43  per  cent. 
At  I30°-I35°  the  loss  was  24-19  per  cent. 
Above  1 35°  decomposition  commenced,  showing  it  to  be  impos- 
sible to  separate  the  last  trace  of  water  without  decomposition. 
Following  these  experiments,  investigation  was  made  upon  six 
samples,  all  of  which  were  collected  without  discrimination  from 
reputable  houses. 
All  were  subjected  to  the  qualitative  tests  of  the  U.S.P.,  after 
