26o.  A  Thermometric  Stirring  Rod.       {Am  May'if96arm' 
A  THERMOMETRIC  STIRRING  ROD. 
By  Charges  H.  UWau. 
For  some  time  past  there  has  been  in  use,  in  the  laboratory  where 
the  writer  is  engaged,  a  convenient  form  of  stirring  rod,  which 
enables  the  worker  to  note  the  temperature  of  a  liquid  without  the 
necessity  of  using  a  thermometer ;  or,  to  describe  its  functions  more 
•accurately,  it  is  a  tubular  glass  stirring  rod,  containing  a  compound 
of  low  melting  point,  which,  by  its  fusion,  indicates  when  the 
temperature  of  a  liquid  arrives  at  a  certain  point,  above  which  it  is 
not  desired  to  have  it  proceed. 
It  is  believed  that  a  short  description  of  the  form  and  uses  of  this 
appliance  would  be  welcomed  by  many  to  whom  its  use  will  soon 
become  familiar,  and,  by  calling  the  attention  of  others  to  a  few  of 
the  advantages  derived  from  its  use,  it  may  undergo  improvements 
which  will  serve  to  widen  its  field  of  application  and  render  it  of 
greater  value. 
A  Thermometric  Stirring  Rod. 
The  description  of  it  is  as  follows :  A  common  glass  tube  about 
5-5  millimetres  (J^  inch)  in  diameter,  outside  measurement,  and 
1 8  centimetres  (7  inches)  long,  is  sealed  by  fusion  in  the  flame  of  a 
Bunsen  burner,  and  bent  slightly  as  in  the  illustration.  This  is  a 
convenient  shape  for  a  stirring  rod,  being  especially  adapted  for 
removing  the  resinous  deposits  which  sometimes  adhere  to  the 
bottom  of  a  capsule,  as  usually  occurs  in  the  assay  of  opium 
preparations. 
Eeeswax,  paraffin  or  any  other  substance  adapted  to  the  require- 
ments of  the  case,  is  then  carefully  adjusted  to  any  desired  melting 
point  by  the  addition  of  a  substance  which  raises  or  lowers  the 
degree  of  temperature  at  which  it  melts.  The  tube  is  then  filled 
about  three-quarters  full  of  the  compound  by  rolling  fragments  be- 
