ON  A  NEW  FORM  OF  CHLORIDE  OF  SODIUM. 
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ON  A  NEW  FORM  OF  CHLORIDE  OF  SODIUM. 
By  Richard  V.  Tuson, 
Lecturer  on  Chemistry  at  Charing  Cross  Hospital. 
That  chloride  of  potassium,  which  ordinarily  crystallizes  in 
cubes,  is  nevertheless  often  found  as  an  efflorescence  on  various 
vegetable  extracts  assuming  the  acicular  form,  is  well  known. 
Hitherto,  I  believe,  the  corresponding  compound,  chloride  of 
sodium,  has  never  been  observed  in  needle-shaped  crystals,  but 
nearly  always  in  cubes.  Occasionally,  however,  it  deposits  from 
urine  in  octohedra  ;  and  when  a  solution  of  the  salt  in  water  is 
evaporated  at  a  temperature  not  exceeding  14Q  F.,  it  crystal- 
lizes in  hexagonal  tables  (Ehrenberg),  which  contain,  according 
to  Fuchs,  six  equivalents,  but  according  to  Mitscherlich,  four 
equivalents  of  water  of  crystallization.  At  temperatures  above 
14p  F.  these  hexagonal  crystals  lose  their  water  of  crystalliza- 
tion, and  are  resolved  into  a  congeries  of  minute  cubes.  Chloride 
of  sodium,  it  is  also  stated,  may  be  obtained  in  large  oblique 
rhombic  prisms,  having  the  formula  Na  Cl.-f-4Aq.  They 
effloresce  in  air  below  32Q  F.  (Mitscherlich),  deliquesce  (?  efflo- 
resce) in  air  above  32°  F.  (Fuchs),  and  leave  a  powder  of  small 
cubes. 
Lately,  on  opening  a  tightly-fitting  tin  box  in  which  a  quan- 
tity of  salmon-roe  paste  had  been  allowed  to  remain  for  nearly 
three  years,  it  was  found  that  the  organic  matter  was  covered 
by  an  efflorescence  of  acicular  crystals.  One  of  my  pupils 
collected  some  of  these  crystals,  analyzed  them,  and  pronounced 
them  to  consist  entirely  of  chloride  of  sodium.  As  I  had  never 
heard  of  chloride  of  sodium  crystallizing  in  needles,  their  ex- 
amination was  repeated,  but  still  the  same  results  were  obtained. 
Some  of  the  crystals  were  next  dissolved  in  water,  and  the  solu- 
tion produced  submitted  to  spontaneous  evaporation,  when  the 
whole  of  the  salt  deposited  in  the  ordinary,  or  cubical  form. 
This  result,  therefore,  fully  confirms  the  conclusions  deduced 
from  analysis.  The  crystals,  some  of  which  are  nearly  half  an 
inch  long,  appear  to  be  rectangular  prisms,  terminated  by  four- 
sided  pyramids.  They  are  beautifully  clear,  transparent,  color- 
less, elastic,  longitudinally  and  transversely  striated,  and  many 
are  bent  or  contorted  in  a  manner  similar  to  the  native  hydrated 
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