Am.  Jour.  Pharm. 
Dec,  1 918. 
Nucleic  Acid. 
877 
larger  quantity  if  available)  are  heated  in  a  boiling  water-bath  for 
two  hours  with  40  Cc.  of  10  per  cent,  sulphuric  acid  (or  a  propor- 
tionately larger  quantity  if  more  than  10  Gm.  are  taken)  in  a  small 
flask  fitted  with  an  air  condenser.  At  the  end  of  this  time  strong 
ammonia  is  added  to  the  hot  solution  in  the  flask  until  the  liquid 
contains  an  excess  of  about  2  per  cent.  The  guanine  is  precipitated 
in  a  granular  form,  the  adenine  remaining  in  solution.  After  filter- 
ing and  washing  with  1  per  cent,  ammonia,  the  guanine  is  dissolved 
in  the  smallest  possible  quantity  of  dilute  sulphuric  acid,  decolorized 
if  necessary  by  means  of  a  little  animal  charcoal,  and  the  base  pre- 
cipitated again  from  the  colorless  solution  by  the  addition  of  an  ex- 
cess of  ammonia.  The  purified  base  may  then  be  converted  into  the 
hydrochloride,  which  crystallizes  very  readily  and  may  be  easily 
identified  by  the  application  of  any  of  the  well-known  tests.  The 
ammoniacal  filtrate  from  the  guanine,  together  with  the  ammoniacal 
washings,  is  acidified  with  sulphuric  acid,  heated  to  boiling,  and  the 
adenine  precipitated  as  a  cuprous  compound  by  the  addition  of  a  10 
per  cent,  solution  of  copper  sulphate."  Inasmuch  as  the  solution 
contains  the  carbohydrate  ribose,  it  is  not  necessary  to  add  sodium 
bisulphite  for  the  purpose  of  reducing  the  cupric  compound.  The 
adenine-copper  compound  is  suspended  in  hot  water,  decomposed 
with  sulphuretted  hydrogen,  and  the  filtrate  from  the  copper  sulphide 
evaporated  to  dryness  on  the  water-bath.  The  residue,  consisting 
of  nearly  pure  adenine,  is  dissolved  in  5  per  cent,  of  sulphuric  acid, 
and  the  adenine  sulphate,  which  is  readily  soluble  in  hot,  but  very 
slightly  soluble  in  cold  water,  allowed  to  crystallize.  The  usual  tests 
can  then  be  applied. 
The  following  is  an  outline  of  the  procedure  to  be  adopted  for 
the  examination  of  nucleic  acid,  with  the  object  of  ascertaining  its 
purity  and  quality. 
The  acid  should  be  white  or  at  the  most  have  a  very  faint  buff 
color.  It  should  be  completely  soluble  in  an  aqueous  solution  of 
sodium  acetate  or  in  dilute  solutions  of  ammonia  or  of  sodium  or 
potassium  hydroxides.  The  solutions  in  these  reagents  should  be 
bright  and  almost  colorless.  When  a  few  drops  of  hydrochloric  acid 
are  added  to  a  solution  of  the  sodium  salt  in  water,  the  acid  should 
be  precipitated  as  a  white  curdy  substance,  and  on  the  further  addi- 
tion of  a  large  excess  of  the  hydrochloric  acid  this  should  dissolve 
completely.  An  aqueous  solution  of  the  sodium  salt  should  give  with 
