248 
Determination  of  Glycerin. 
f  Am.  Jour.  Pharm. 
1       May,  1866. 
solubility  of  caffeine,  pharmacists  are  sometimes  perplexed  when 
making  a  solution  for  hypodermic  use.  Tanret  recommends  the  fol- 
lowing: — R.  Sodii  benzoatis,  2*95;  caffeini,  2'50;  aquas  dest.,  10  c.c. 
Mix  the  benzoate  of  sodium  and  cafTeine  in  a  mortar  and  add  the 
water ;  filter.  Benzoate  of  sodium  is  preferable  to  the  salicylate.  If 
any  trace  of  iron  is  present,  salicylate  of  sodium  would  form  a  rose- 
colored  solution. — Repertoire  cle  Pharmacie,  March,  1886,  p.  119. 
Preparation  of  Guaranine. — Rochefontaine  and  Gusset  give  the 
following  formula  for  making  guaranine : — 5  gm.  of  powdered 
guarana  are  mixed  with  1  gm.  of  calcined  magnesia,  and  the  whole 
moistened  with  water ;  after  twenty-four  hours  the  mass  is  exhausted 
with  40  gm.  of  boiling  chloroform,  the  chloroform  distilled  or 
evaporated  and  the  residue  treated  with  boiling  water,  filtered  and 
evaporated  over  sulphuric  acid.  After  several  recrystallizations, 
colorless  crystals  of  guaranin  are  obtained.1  Yield  =  4*5  per  cent. — 
Chemischtechnischer  Central  Anzeie/er,  iv,  p.  322. 
Manufacture  of  Aluminium  by  Electrolysis. — A  saturated  solution 
of  aluminium  sulphate  and  a  solution  of  sodium  chloride,  separated 
by  means  of  a  porous  vessel,  are  acted  on  by  a  current  from  6  or  7 
Yoltas  and  4  Amperes.  The  double  chloride  of  sodium  and 
aluminium  formed  is  decomposed,  the  aluminium  settling  on  the  nega- 
tive electrode.  This  method  can  be  employed  for  aluminium  plating 
and  also  for  obtaining  aluminium  by  a  cheap  process. —  Chemisch- 
teehnischer Central  Anzeic/er,  iv,  p.  322. 
THE  DETERMINATION  OF  GLYCERIN. 
By  'William  Fox  and  J.  A.  Wanklyn 
During  an  investigation  on  the  constitution  of  oils  and  fats,  with 
which  we  are  engaged,  it  became  necessary  to  make  a  number  of  gly- 
cerin determinations,  and  as  experiment  proved  the  ordinary  methods 
to  be  inaccurate,  we  worked  out  the  method  given  below,  and  which  is 
based  on  the  fact  that  glycerin,  oxidized  with  permanganate  of  potash 
in  a  strongly  alkaline  solution,  gives  oxalic  acid  according  to  the 
equation  C3Hs03-06=aHA-C02-3H20. 
The  oxalate  can  be  precipitated  by  a  lime  salt,  and  the  amount  of 
1  A  much  simper  process  for  the  preparation  of  enffeine  from  guarana  ^vas 
recommended  by  Dr.  F.  V.  Greene  (1S77)  and  by  Mr.  Feemster  (1882),  and  con- 
sists in  boiling  the  guarana  with  oxide  of  lead,  adding  a  small  quantity  of  basic 
lead  acetate,  and  evaporating  the  nitrate. — See  Am.  Jour.  Phar.,  1877,  p.  332, 
and  1882,  p.  523.—  Editor. 
