VARIETIES. 
81 
Faraday's  mean  estimate  of  one  charge  of  his  batter y  as  the  basis  of  calcula- 
tion."— Ibid. 
Artificial  Formation  of  Minerals. — M.  Becquerel  has  recently  made  some 
valuable  observations  on  the  artificial  formation  of  minerals  by  electro- 
chemical action.  In  detailing  his  experiments,  he  states  that  sulphuret  of 
lead  was  made  to  act  upon  a  saturated  solution  of  sulphate  of  copper  and  of 
chloride  of  sodium,  diluted  with  an  equal  volume  of  distilled  water,  with  a 
view  of  obtaining  compounds  of  lead,  analogous  to  the  compounds  of  the 
same  metal  existing  in  a  natural  state.  There  were  found,  either  upon  the 
pieces  of  sulphuret  of  lead,  or  at  the  bottom,  or  in  the  partitions  of  the 
vessels — 
1.  Chloride  of  sodium,  in  cubes,  cubic  octohedrons,  and  even  octohedrons, 
of  great  transparency,  and  very  definite  in  form. 
2.  Chloride  of  lead,  in  needles  and  cubes,  slightly  yellowish,  and  very 
perfect  in  form. 
3.  Sulphate  of  lead,  in  cuneiform  octohedrons,  precisely  resembling  in 
form  the  crystallized  sulphate  of  lead  from  Anglesey. 
4.  Chlorosulphate,  in  needles. 
5.  Basic  chloride,  in  microscopic  crystals, 
6.  Sulphuret  of  copper,  black  in  color,  without  any  appearance  of  crystal- 
lization. In  some  of  the  vessels  there  were  formed  only  chloride  and  chloro- 
sulphate of  lead  ;  in  others,  chloride  and  sulphate ;  which  depended,  no 
doubt,  upon  the  proportions  of  the  sulphate  of  copper  and  of  chloride  of 
sodium,  and  the  density  of  the  solutions.  A  voltaic  couple,  formed  of  a 
piece  of  galena  surrounded  by  a  platinum  wire,  placed  in  a  saturated  solu- 
tion of  common  salt  and  sulphate  of  copper,  diluted  with  three  volumes  of 
water,  gave  rise  to  the  formation  of  a  considerable  quantity  of  crystallized 
chloride  of  lead,  in  cubes,  without  any  other  product ;  they  were  similarly 
deposited,  though  a  little  larger,  upon  a  fragment  of  malachite  which  was 
placed  in  the  solution.  He  supposes  that  similar  reactions  to  these  may 
occasionally  take  place  on  a  large  scale  throughout  nature,  causing  the 
natural  formation  of  some  minerals. — Ibid. 
Solubility  of  Common  Salt. — It  has  been  heretofore  an  established  law, 
that  pure  chloride  of  sodium  is  equally  soluble  in  both  hot  and  cold  Water, 
Fehling,  who  has  recently  reinvestigated  this  subject,  arrives  at  the  conclu- 
sion, that  it  is  more  soluble  in  boiling  than  in  cold  water.  He  finds  that 
one  hundred  parts  of  a  saturated  solution  of  salt  at  54°  Fahr.  contains 
26.423  parts  of  chloride  of  sodium,  consequently  one  hundred  parts  of  water 
will  dissolve  35;91  parts  of  salt  at  that  temperature ;  and  that  one  hundred 
parts  of  a  boiling  saturated  solution  of  salt  contains  28.53  parts  of  chloride 
of  sodium,  therefore  one  hundred  parts  of  boiling  water  dissolves  39.02 
parts  of  chloride  of  sodium. — Ibid,  March  1852,  from  Annalen  dor  Chemi® 
and  Pharmacie. 
