Am.  Jour.  Pharm. 
Nov.,  1918. 
Diphtheria  Antitoxin. 
77i 
saturation  with  (NH4)2S04  contains  no  antitoxins,59  while  it  is 
found  in  the  precipitate.  Na2S04  (9-12  per  cent.)  precipitates 
50  per  cent,  of  the  antitoxin  from  serum.  Na2S04  is  used  in  place 
of  (NH4)2S04  as  a  precipitant  for  the  antitoxin  in  serum,  partly 
because  (NH4)2S04  is  reduced  to  NH3  by  some  albumins.  It  has 
about  the  same  precipitating  value  as  (NH4)2S04.60  Dilute  sera 
reacts  differently  with  Na2S04  than  concentrated  ones. 
Salts  with  bivalent  cations,  i.  e.,  Ca(C2H302)2  10  per  cent,  or 
MgS04  have  no  deleterious  effect  on  the  antitoxin  or  its  combination 
with  the  toxin  in  serum.  The  colloids  of  the  serum  may  perhaps 
protect  the  antitoxin  from  the  action  of  calcium.61  MgS04  at  30- 
370  C.  precipitates  only  50  per  cent,  of  the  antitoxin  from  serum,62 
but  according  to  Freund  and  Sternberg  the  filtrate,  after  MgS04  pre- 
cipitation, contains  no  antitoxin.  These  experiments  were  carried 
on  at  17-180  C.63    Strontium  salts  give  negative  results.64 
Zinc  salts  are  said  to  be  especially  suited  for  precipitation  of  the 
antitoxin.  According  to  Brieger  and  Boer,  ZnS04  and  ZnCl2  can 
be  used  for  separating  it  quantitatively.  The  Zn  precipitate  can  be 
dissolved  in  water  by  means  of  weak  NaOH  (one  drop  normal  solu- 
tion in  20  cc.  H20)  and  then  C02  can  be  used  to  precipitate  the  zinc. 
However  by  this  method  there  is  a  question  if  all  of  the  zinc  is  re- 
moved. In  case  ZnS04  has  been  used,  the  antitoxin  remains  in  the 
precipitate,  while  if  ZnCl2  has  been  used,  it  goes  into  the  filtrate. 
Freund  and  Sternberg  obtained  no  precipitate  of  antitoxin  with 
ZnS04  or  ZnCl2  after  the  use  of  potassium  alum  and  aluminium 
sulphate  even  though  the  solution  had  been  dialyzed  eight  days. 
They  claim  that  zinc  hydrate  precipitates  antitoxin.  Cobalt  salts 
gave  negative  results  with  antitoxin.65 
The  precipitate  of  iron  salts  with  alkali  carries  antitoxin  me- 
chanically,66 but  it  is  difficult  to  free  it.67  The  precipitate  from  the 
serum  by  K4Fe'Cy6  and  ZnS04  {%.  e.,  ferro-cyanide  of  zinc)  contains 
59  Freund  and  Sternberg. 
60  Brunner,  J.,  and  Pinkus,  S.  N.,  Biochem.  Zeits.,  Vol.  5,  p.  381,  1907. 
61  Pick  and  Schwarz.    See  also  Osterhout,  W.  J.  U.,  Bot.  Gas.,  1915,  59, 
316. 
62  Brieger  and  Boer. 
63  See  also  Brodie. 
64  Freund  and  Sternberg. 
65  Freund  and  Sternberg. 
66  Freund,  E.,  and  Sternberg,  C,  Zeits.  f.  Hyg.,  Vol.  31,  p.  429,  1899. 
67  In  this  connection,  see  Brossa,  A.,  and  Freundlich,  H.,  Zeits.  Phys. 
Chem.,  89,  p.  306. 
