430 
ON  A  NEW  TEST  FOR  POTASH. 
solutions  together.  The  quantity  of  potash  solution  employed 
in  each  experiment  was  20  fluid  grains. 
With  the  first  sulphate  of  potash  solution,  tartaric  acid  gave 
a  precipitate  immediately,  after  much  agitation ;  bitartrate  of 
soda  gave  with  the  same  solution  a  copious  precipitate  after  a 
very  slight  agitation. 
With  the  second  solution,  tartaric  acid  gave  a  slight  precipi- 
tate after  much  agitation,  and  after  standing  twenty-four  hours ; 
bitartrate  of  soda  gave  with  the  same  solution  a  plentiful  precip- 
itate immediately  after  it  had  been  well  agitated. 
With  the  third  solution,  tartaric  acid  gave  no  precipitate  even 
after  standing  twenty-four  hours  ;  bitartrate  of  soda  gave  a  dis- 
tinct precipitate  after  much  agitation  almost  immediately. 
With  the  fourth  solution,  tartaric  acid  gave  no  precipitate 
even  after  long  standing ;  bitartrate  of  soda  gave  a  slight  tur- 
bidity after  much  agitation  and  standing  a  short  time  ;  the  quan- 
tity did  not  increase  by  long  standing. 
In  order,  still  further,  to  prove  the  greater  delicacy  of  bitar- 
trate of  soda,  I  added  tartaric  acid  to  a  solution  of  a  salt  of 
potash,  and  after  agitating  it  very  well  I  allowed  it  to  stand  for 
twenty-four  hours ;  I  then  filtered  off  from  the  bitartrate  of  pot- 
ash which  had  been  formed,  and  added  to  the  filtrate  a  solution 
of  bitartrate  of  soda  and  agitated,  when  an  immediate  precipitate 
of  bitartrate  of  potash  was  produced. 
The  acids  may  differ  as  to  their  capability  of  dissolving  bitar- 
trate of  potash  ;  it  is  therefore  possible  that  if  I  had  employed 
nitrate  of  potash  or  chloride  of  potassium  instead  of  sulphate  of 
potash  in  the  experiments,  the  difference  between  the  two  tests, 
tartaric  acid  and  bitartrate  of  potash,  might  not  have  been  quite 
so  marked  as  in  the  experiments  I  have  given. 
I  need  scarcely  remark  that  bitartrate  of  soda  cannot  replace 
tartaric  acid  as  a  test  when  the  solution  to  be  tested  contains  a 
free  alkali,  because  bitartrate  of  potash  is  soluble  in  free  alka- 
lies ;  but  if  the  other  bases  are  sought  for,  the  solution  cannot 
be  alkaline  when  we  arrive  at  the  examination  for  potash,  and  it 
is  not  often  that  we  have  to  deal  with  an  alkaline  solution,  even 
when  potash  is  the  only  base  that  is  looked  for. 
This  investigation  was  carried  out  in  the  laboratory  of  this 
Institution  under  the  direction  of  Mr.  Galloway. — Chemical 
G-azette,  June  1,  1858. 
