CHEMICAL  NOTES. 
521 
CHEMICAL  NOTES. 
By  John  M.  Maisch. 
Chloride  of  Potassium. — Chemical  works  state  that  this  salt 
crystallizes  in  cubes,  sometimes  elongated  to  prisms,  and  rarely 
in  octohedrons.  Several  years  ago,  when  evaporating  a  con- 
siderable quantity  of  a  solution  of  this  salt,  it  occurred  to 
me  to  ascertain  under  what  circumstances  it  might  be  made  to 
assume  these  different  shapes.  I  exposed  the  solution  to  the 
heat  of  a  sand  bath,  taking  care  not  to  raise  the  temperature  to 
the  boiling  point  of  the  liquid.  In  this  condition  it  separated 
perfect  cubes.  As  soon  as  they  commenced  to  grow  together, 
the  solution  was  decanted  and  allowed  to  cool  slowly  at  a  sum- 
mer temperature.  The  chloride  now  crystallized  in  four-sided 
prisms  which  were  drained  on  a  funnel,  and  the  clear  liquid  set 
aside  over  night,  when  the  salt  was  found  to  have  crystallized  in 
irregular  pyramids,  composed  of  numerous  small  crystals. 
Since  that  time  I  have  repeated  the  experiment  on  several 
occasions,  always  with  the  same  result.  In  no  instance  did  I 
obtain  octohedrons,  which  are  stated  to  be  produced  from  alka- 
line solutions.  I  took  good  care  to  have  my  liquid  in  all  cases 
perfectly  neutral,  and  to  cool  it  very  slowly  upon  a  bed  of  straw 
or  saw  dust,  and  in  a  room  not  affected  by  sudden  changes  of  the 
atmosphere. 
The  cubes  are  semi-transparent,  sometimes  nearly  opaque  and 
perfect  when  single,  but  usually  deformed  on  one  side  when 
grown  together.  The  prisms  are  four-sided,  rectangular,  trans- 
parent, and,  as  seen  under  a  magnifier,  do  not  consist  of  cubes 
grown  together  in  the  direction  of  one  axis;  when  exposed  to 
heat,  they  decrepitate  below  their  fusing  point,  losing  a  lit- 
tle hygroscopic  water,  and  break  chiefly  in  the  direction  of  their 
long  axis,  resulting  in  smaller  prisms  and  needles  but  not  in  cubes. 
The  pyramids  are  an  irregular  section  of  a  cube,  and  are  com- 
posed of  a  conglomeration  of  the  rectangular  prisms  joined  to- 
gether by  their  prismatic  planes ;  the  end  planes  are  cut  off  at 
an  angle  of  about  45°,  to  which  the  planes  of  a  layer  of  prisms, 
cut  off  in  a  similar  oblique  direction,  are  joined  so  as  to  form  a 
right  angle.    The  space  between  these  two  layers  is  filled  up 
