118 
ON  TESTS  FOU  THE  PURITY  OF  GLYCERIN. 
comes  rather  strong  on  rubbing  it  between  the  hands,  particularly 
near  the  fire.  The  specific  gravity  at  63°  F.  was  1*252  of  No.  1, 
1-253  of  No,  2,  1-250  of  No.  3  and  1-241  of  No.  4. 
No.  4,  when  diluted,  caused  precipitates  with  several  reagents 
and  was  set  aside.  The  other  samples  were  subjected  to  the  same 
tests,  under  precisely  the  same  conditions.  Half  a  fluid-ounce 
of  each  was  diluted  with  sufficient  distilled  and  perfectly  pure 
water  to  make  five  fluid-ounces. 
Blue  and  red  litmus  paper  was  not  affected.  With  sulphuretted 
hydrogen  and  sulphide  of  ammonium,  they  remained  unchanged  ; 
the  addition  of  a  trace  of  solution  of  acetate  of  lead  caused  a 
brown  coloration. 
Subacetate  of  lead,  unchanged ;  the  addition  of  a  little  soap, 
tannin  or  sulphuric  acid  produced  a  turbidity. 
Chloride  of  calcium,  no  change  ;  a  minute  quantity  of  oxalate 
of  soda  rendered  the  liquid  turbid. 
Ferrocyanide  of  potassium,  undisturbed;  a  trace  of  proto-sul- 
phate  of  iron  yielded  a  bluish  color. 
Oxalate  of  soda,  unchanged  with  2  and  3  ;  No.  1  produced  a 
very  slight  deposit  on  the  side  of  the  test  tube  after  rubbing  it 
with  a  glass  rod ;  on  the  addition  of  a  little  chloride  of  calcium, 
a  white  turbidity  was  instantaneously  produced. 
Nitrate  of  baryta,  precisely  as  in  the  foregoing  experiment ; 
a  white  turbidity  was  occasioned  by  dilute  sulphate  of  soda. 
Alkaline  solution  of  copper  had  no  effect  on  boiling  ;  after  the 
addition  of  a  trace  of  honey,  and  boiling,  red  suboxide  of  cop- 
per was  precipitated. 
Ak aline  solution  of  bismuth,  on  boiling,  produced  no  change  ; 
but  boiling  with  a  little  honey,  yielded  a  black  precipitate. 
Nitrate  of  silver  had  no  effect  on  Nos.  2  and  3,  either  in  the 
cold  or  on  heating  it  to  the  boiling  point.  With  No.  1,  a  white 
turbidity  was  occasioned,  and  when  heated  to  boiling,  a  black 
precipitate  was  thrown  down  and  the  liquid,  though  transparent, 
was  of  a  blackish  brown  color.  No.  4  yielded  at  once  a  dense 
turbidity  and  soon  a  white  precipitate ;  after  heating  to  boiling, 
the  latter  was  of  a  grey  color,  while  the  supernatant  liquid  had 
acquired  a  fine  rose  color.  The  white  turbidity  in  Nos.  1  and  4 
was  not  removed  by  nitric  acid,  but  ammonia  rendered  the  liquid 
clear. 
