68 
Chemical  Notes. 
f  Am.  Jour.  Pharm. 
t      Feb.,  1882. 
Dissolve  the  citric  acid  in  20  fluidounces  of  hot  water ;  add  the 
magnesia,  and  when  solution  is  effected  add  the  sugar,  then  the  bicar- 
bonate of  sodium,  the  oil  of  lemon  and  cold  water.  Filter,  and  of 
this  put  10  fluidounces  in  a  suitable  bottle,  with  40  grains  of  bicarbon- 
ate of  potassium,    Cork  tightly  and  tie  over  as  usual. 
CHEMICAL  NOTES. 
By  Prof.  Samuei^  P.  Sadtler,  Ph.D. 
Inorganic  Chemistry. —  On  the  freezing  point  of  Sulphuric  Acid 
of  different  degrees  of  concentration. — Prof.  G.  Lunge  has  made  a  series 
of  careful  experiments  on  the  question  of  the  degree  of  cold  necessary 
to  bring  about  the  formation  of  crystals  in  sulphuric  acid  of  differ- 
ent specific  gravities.  According  to  Marignac,  pure  sulphuric  acid, 
H2SO4  (frequently  called  monohydrated  sidphuric  acid),  fuses  at 
-HlO*5°C.;  the  strongest  acid  obtainable  by  evaporation  or  boiling, 
which  contains  98  to  99  per  cent,  of  monohydrated  acid  at  the  most, 
being  said  to  deposit  these  crystals  of  monohydrate  when  cooled  to 
0°C.,  although  frequently  that  point  is  reached  without  any  change 
whatever.  It  is  known  too  that  the  common  strong  sulphuric  acid  of 
commerce,  that  of  66°  Baume,  which  contains  95  to  96  per  cent,  of 
monohydrated  acid  cannot  be  brought  to  solidify  even  by  a  freezing 
mixture.  However,  the  so-called  second  hydrate,  H2S04-f~H20,  repeat- 
edly crystallizes  at  -|~8°C.,  and  this  often  happens  in  practice.  Acids 
which  approximate  this  composition  (the  second  hydrate  contains 
84*5  per  cent.  H2SO^,  and  has  a  sp.  gr.  of  1*778  or  63*2°  Baume),  when 
exposed  to  the  frost  in  winter  time  may  burst  the  carboys. 
Prof.  Lunge  has  made  a  series  of  tests  on  acids  of  different  strength, 
using  a  mixture  of  three  parts  ice  and  one  part  common  salt  in  which 
the  thermometer  sank  to  — 20°C.  The  results  are  appended  in  tabu- 
lar form  : 
Sp.  Gr.atSQOC. 
Degree  Baume. 
Freezing-Point. 
Fusing-Poi] 
1-671 
58- 
liquid  at  — 20°C 
1-691 
59- 
1-712 
60-05 
1-727 
60-75 
—7-5° 
—7-5° 
1-732 
61- 
—8-5° 
—8-5° 
1-749 
61-8 
—0-2° 
+4-5° 
1-767 
62-65 
+1-6° 
+6-5° 
1-790 
63-75 
+4-5° 
+8-  ° 
1-807 
64-45 
—9-0° 
—6-  ° 
1-822 
65-15 
liquid  at  — 20°C 
1-842 
56- 
— Ber.  der  Ohem.  Ges.,  xiv,  p.  2649. 
