Am.  Jour.  Pharm. 
Sept.,  1880. 
Chemical  Notes. 
465 
CHEMICAL  NOTES. 
By  Prof  Samuel  P.  Sadtler,  Ph.D. 
Inorganic  Chemistry. —  On  the  Theory  of  Freezing-mixtures. — A. 
Ditte  shows  that  in  cases  where  a  reduction  of  temperature  follows  the 
mixing  of  a  hydrated  salt  and  an  acid  an  anhydrous  salt  has  been  pro- 
duced, and  a  large  amount  of  water  of  hydration,  previously  existing  in 
the  solid  form,  becomes  free  and  is  liquefied.  Thus,  the  reduction  of 
temperature  following  when  Glauber's  salt  with  muriatic  acid  is  explained 
by  the  following  reaction: 
Na2S04.ioH204-HCl==NaCl+NaHSo,+  ioH20. 
The  author  therefore  sought,  in  verification  of  this  hypothesis,  to 
produce  a  freezing  mixture  by  rubbing  together  two  salts  which,  while 
possessing  nearly  equal  thermo-chemical  value  (so  that  no  heat  would  be 
developed  by  their  reaction  upon  each  other),  should  liberate  in  their 
mutual  decomposition  water  of  hydration,  which  would  then  have  to 
become  liquid.  He  found  as  an  actual  fact  that  the  rubbing  together 
of  ammonium  nitrate  and  Glauber's  salt  produced  a  diminution  of  tem- 
perature of  about  20°C.,  ammonium  nitrate  and  sodium  phosphate 
together  a  loss  of  j8°C.,  and  ammonium  nitrate  and  soda  a  loss  of 
25°C. — Compt.  Rend.^  No,  90,  pp.  1191  and  1282. 
Detection  and  Determination  of  Chlorine  in  Presence  of  Bromine  and 
Iodine. — G.  Vortman  has  discovered  a  method  by  means  of  which  even 
small  quantities  of  chlorine,  along  with  the  other  halogens,  can  be  easily 
and  quickly  detected.  It  depends  on  the  different  behavior  of  the 
chlorides,  bromides  and  iodides  with  peroxides  of  manganese  and  lead, 
in  presence  of  acetic  acid. 
Iodides  are  partially  decomposed  by  the  above-mentioned  peroxides,, 
even  in  neutral  solutions,  and  if  they  are  boiled  with  the  addition  of 
acetic  acid  the  iodine  is  completely  eliminated.  Lead  peroxide  oxi- 
dizes a  part  of  the  iodine  to  iodic  acid,  but  with  manganese  peroxide  no 
iodic  acid  is  formed. 
In  a  neutral  solution  bromides  are  not  decomposed  either  by  man- 
ganese or  lead  peroxide.  In  an  acetic  acid  solution  the  lead  peroxide 
only  acts,  bromine  escapes,  but  bromic  acid  is  formed  only  if  bromides 
are  present  in  considerable  quantities.  Manganese  peroxide  has  no 
action  in  the  acetic  acid  solution,  even  on  prolonged  heating.  Chlorides 
are  not  attacked  by  either  of  the  peroxides  in  presence  of  acetic  acid. 
In  testing  for  chlorides  in  presence  of  bromides  or  iodides,  it  is  suffi- 
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