.Am.  Jo«r.  Pharni. ) 
June,  1881.  j 
Chemical  Notes. 
293 
but  no  ap])licatioii  of  lieat  brings  its  temperature  above  zero  C. — Bei\ 
Chem.  Gcs.,  xiv,  p.  718,  and  Nature,  March  31st,  1881. 
A  Neiu  Method  for  the  Manufacture  of  Potashes. — Potassium  chlor- 
ide, that  abundant  product  of  the  Stassfurt  salt  deposit,  can  be 
changed  direct  into  the  carbonate,  according  to  E.  Engel,  by  the  fol- 
lowing procedure :  Magnesia  orjnagnesium  carbonate  is  added  to  the 
aqueous  solution  of  potassium  chloride  and  the  mixture  is  then 
treated  with  carbon  dioxide  gas.  Magnesium  bicarbonate  forms  at 
first,  this  dissolves  and  then  reacts  with  the  }3otassium  chloride  to  form 
magnesium  chloride  and  a  crystalline  double  salt  (MgCOgjKHCOg) 
which  separates  out  according  to  the  following  reaction  :  SMgCOg-f 
2KCl-fC02=2(MgC03,KHC03)  +  MgCl2.  This  double  salt,  which 
had  already  been  prepared  by  Berzelius  and  St.  Clair  Deville  from 
magnesia  and  potassium  bicarbonate,  is  decomposed  by  heating  with 
water  into  potassium  carbonate  and  magnesium  carbonate  which 
separates  out.  In  this  process  a  part  of  the  potassium  chloride  escapes 
decomposition.  The  mother  liquor  of  the  double  salt  is  therefore 
evaporated,  and  from  it  either  carnallite  or  potassium  chloride  will 
<3rystallize  out.  The  process  is  patented  and  is  now  being  carried  out 
on  a  large  scale  at  Montpellier. — Compt.  Rend.,  92,  p.  725. 
Preparation  of  Hydrochloric  Acid. — Ernest  Solvay,  of  Brussels, 
has  taken  out  an  English  patent.  No.  837,  for  the  preparation  of 
hydrochloric  acid  gas.  His  method  is  based  upon  the  fact  that  a  con- 
centrated aqueous  solution  of  calcium  chloride  holds  back  water  at  a 
temperature  at  which  it  will  not  absorb  hydrochloric  acid  gas.  If  a 
mixture  of  hydrochloric  acid  gas  and  air  is  therefore  led  into  a  con- 
centrated solution  of  calcium  chloride,  the  air  escapes  while  the  hydro- 
•chloric  acid  and  water  are  held  back.  When  the  solution  is  heated, 
the  hydrochloric  acid  gas  escapes  in  a  perfectly  dry  state.  Wlien  the 
hydrochloric  acid  gas  is  mixed  only  with  steam  or  vapor  of  water,  the 
calcium  chloride  solution  is  simply  kept  at  a  temperature  at  which  it 
holds  the  water  but  allows  the  dry  hydrochloric  acid  gas  to  escape. 
The  gradual  dilution  of  the  calcium  chloride  solution  is  counteracted 
by  addition  of  dry  calcium  chloride  from  time  to  time. 
From  aqueous  hydrochloric  acid  the  gas  is  also  liberated  in  a  dry 
.state  on  addition  of  calcium  chlorideand  heating.  —  Chem.  Indus. ^ 
April,  1881,  p.  117. 
Production  of  Alkaline  Cyanides.  —  \"ictor  Alder,  of  Vienna,  has 
Jtaken  out  a  German  patent,  No.  12,351,  of  11th  of  Marcli,  1880,  for 
