SYRUP  PHOSPHATES  OF  IRON,  QUINIA  AND  STRYCHNIA.  325 
here  represents  only  575*54  gr.  of  metaphosphoric  acid, 
FeO,  2  HO  P05  :  P05  HO  :  :  899-28  :  (  ) 
125  :       80     :  :  899-28  :  575-54 
which  is  all  that  is  requisite  to  form  a  soluble  salt ;  the  remain- 
ing 424-46  gr.  of  metaphosphoric  acid  must  therefore  be  excess. 
To  convert  1000  gr.  of  protosulphate  of  iron  into  superphos- 
phate, 347-73  gr.  of  tribasic  phosphate  of  lime,  3CaO  P05,  also  in 
the  condition  of  superphosphate  (CaO  2HO  P05,  787-44  gr.)  must 
be  employed  for  the  removal  of  the  sulphuric  acid,  as  sulphate 
of  lime  (CaO,  S03  2  HO). 
CaO,  2  HO  P05  +  FeO  S03  7  HO  =  CaO,  S03  2  HO  + 
FeO  2  HO  P05  +  5  HO. 
3(FeO,  S03  7  HO)  :  3  CaO,  P05  :  :  1000  :  (  ) 
417  :       155        :  :  1000-:  347-73 
3  CaO  P05  :  3(CaO  2  HO  P05  :  :  347-73  :  (  ) 
155     :  351  :  :  347-73  :  787-44 
But  347*73  gr.  of  tribasic  phosphate  of  lime  already  contains 
179*47  gr.  of  metaphosphoric  acid, 
3  CaO  P05  :  P05  HO  :  :  347-73  :  (  ) 
155  :  80  :  :  347*73  :  179*44 
so  then  only  820*53  gr.  additional  of  metaphosphoric  acid  will 
be  necessary  to  complete  the  required  1000  gr.  In  this  820*53 
gr.  of  metaphosphoric  acid,  first  dissolved  in  5  f,5  of  water,  dis- 
solves the  tribasic  phosphate  of  lime  with  the  aid  of  heat ;  to 
the  hot  solution  then  add  the  protosulphate  of  iron  in  powder ; 
when  this  has  been  dissolved  and  decomposed,  filter  to  separate 
the  insoluble  sulphate  of  lime,  and  when  the  liquid  has  ceased  to 
pass,  wash  the  residue  several  times  with  small  quantities  of 
water.  The  filtrate  now  contains  the  whole  of  the  iron  as  super- 
phosphate, together  with  the  excess  of  metaphosphoric  acid. 
Mr.  Aitken's  formula  for  24  fj  of  the  syrup,  provides  as  fol- 
lows : 
Protosulphate  of  Iron, 
300  gr. 
Phosphate  of  Soda, 
480  gr. 
Sulphate  of  Quinia, 
192  gr. 
Strychnia,  .... 
6  gr. 
Sugar,  
14.3 
Diluted  Phosphoric  Acid,  U.  S., 
14  il 
