AmMJa0rc^h,m6!:m•}      Sulphurous  Acid  Gas  in  Solution.  151 
ON  THE  SPECIFIC  GRAVITY  OF  SULPHUROUS  ACID 
GAS  IN  SOLUTION. 
By  B.  Gilles  and  A.  Shearer. 
The  authors  have  made  numerous  determinations  to  ascertain  the 
specific  gravities  of  aqueous  solutions  of  sulphurous  acid  gas  (SOa), 
and  the  percentages  of  that  substance  contained  therein.  Their  results 
are  as  follows  : 
Spec.  Grav.  •  Tern.    SO,  in  100  pts.    Spec.  Grav.       Tern.  SO2inl00pts. 
1-0051         15-5°  C.  0-99  1-0399         15-5°  C  8-08 
1-01O2  "  2-05  1-0438  "  8'68 
1.0148  "  2-87  1-0492  "  9*80 
1-0204  "  4-04  1-0541  "  10-75 
1-0252  "  4-99    '  1.059/        12-5°  C.  11'65 
1-0297  "  5-89  T0668         ir0°  C.  13*09 
1-0353  "  7-01 
The  authors  in  cDnclusion  state  that  when  the  determinations  at 
15  5°  C.  and  760  mm.  pressure  were  made,  the  specific  gravity  was 
increased  in  the  proportion  of  O005  for  every  augmentation  of  1 
part  in  100  of  the  quantity  of  sulphurous  acid  gas. 
This  last  statement  is  a  most  important  confirmation  of  the  results 
of  previous  experiments;  and  if  Scott's  determinations  at  15°  C.  and 
Hager's  at  17'5°  C.  (See  National  Dispensatory,  3d  edit,  p.  102)  be 
placed  under  this  rule,  a  curious  uniformity  of  comparative  results  will 
be  observed.  Annali  di  Chim.  Med.  Far.,  1885,  p.  244;  Jour.  Soc. 
Chim.,  iv.,  p.  303.  J.  W.  E. 
DOUBLE  NITRATES  OF  SILVER  AND  THE  ALKALIS. 
By  A.  Ditte. 
When  a  solution  containing  silver  and  potassium  nitrates  is  slowly 
concentrated,  potassium  nitrate  at  first  crystallizes  alone,  but  as  soon 
as  the  liquid  contains  at  least  3  mols.  of  silver  nitrate  for  each 
mol.  of  potassium  nitrate  bulky,  transparent,  right  rhombic  prisms 
are  formed.  These  prisms  are  highly  modified  and  have  the  com- 
position AgN03,KN03.  This  double  salt  is  always  formed  when  a 
solution  of  the  two  nitrates  contains  so  much  of  the  silver  salt  that 
both  nitrates  can  crystallize  simultaneously.  If  the  double  salt  is 
treated  with  water,  the  silver  nitrate  is  gradually  removed. 
Rubidium  nitrate  yields  a  strictly  analogous  double  salt,  and  in  all 
probability  csesium  nitrate  will  behave  in  the  same  way. 
If  a  solution  of  silver  and  ammon'um  nitrates  is  gradually  concen- 
