888      SOLUTION  OF  PYROPHOSPHATE  OF  SODA  AND  IRON. 
remarkable  fact  in  regard  to  it  is  that  it  is  not  saponifiable  by- 
alkalies,  either  at  ordinary  or  boiling  temperatures,  all  experi- 
ments to  that  effect  having  failed.  As  all  fixed  oils,  whether  of 
vegetable  or  animal  origin,  are  saponifiable,  it  is  not  improbable 
that  this  oil  is  of  mineral  origin,  perhaps  approximating  to  the 
so-called  lubricating  oils  obtained  from  lignite,  which  sometimes 
have  a  sp.  gr.  as  high  as  0*960  (Oppler).  My  knowledge  of  these 
oils  is,  however,  but  limited,  and  I  can  therefore  merely  state 
these  facts,  but  shall,  perhaps,  find  time  shortly  to  give  the  sub- 
ject more  attention,  when  I  will  communicate  the  results. 
The  oil  of  lemon  under  consideration  reached  us  through  a 
Chicago  firm,  but  has  not  been  traced  further.  It  was  of  toler- 
ably good  odor,  but  more  viscid  than  the  ordinary  oil  of  lemon, 
and  had  a  sp.  gr.  of  0*890  at  62°  F.,  which  is  considerably 
higher  than  that  of  pure  oil  of  lemon. 
Louisville,  Ky--,  July  llthy  1867. 
ON  A  PERMANENT  SOLUTION  OF  PYROPHOSPHATE  OF 
SODA  AND  IRON. 
By  John  M.  Maisch. 
A  "subscriber"  desires  some  light  regarding  a  heavy  white 
precipitate  which  appears,  on  standing,  in  a  secret  preparation 
styled  Elixir  of  Pyrophosphate  of  Iron  and  Soda.  Having  never 
seen  the  preparation  in  question,  and  not  being  over  anxious  to 
analyze  a  medicine  when  the  so-called  proprietors  withhold  the 
formula  and  modus  operandi,  we  will  endeavor  to  throw  some 
light  on  the  other  desire  of  our  correspondent, — to  obtain  a  work- 
ing formula  for  such  a  preparation.  In  this  connection  it  will 
not  be  amiss  to  give  a  short  historical  sketch  of  our  knowledge 
of  the  pyrophosphates. 
About  forty  years  ago,  S.  Engelhart*  observed  that  albumen 
is  precipitated  by  phosphoric  acid  prepared  by  burning  phospho- 
rus, or  by  heating  the  ordinary  acid  to  redness.  Shortly  after- 
wards, Stromeyer  noticed  that  phosphate  of  soda,  heated  to  red- 
ness, will  precipitate  silver  salts  white,  and  the  same  discovery 
was  made  about  the  same  time  by  Clarke,t  who  applied  to  the 
*  Poggend.  Ann.  ix.  631. 
t  Edinb.  Journ.  of  Science,  vii.  298. 
