Am.  Jour.  Pharm. 
Dec,  1883. 
Calcium  Lactophosphate. 
609 
potassic  molecule  in  which  two  iodine  radicles  are  substituted.  Another 
striking  example  may  be  given  in  the  case  of  crystallized  sodic  sul- 
phate. If  in  an  unduodecimal  molecule  of  water,  HggOii,  we  replace 
O  by  SO4,  we  get  H22O10SO4,  and  if  in  this  we  substitute  H2  by  Nag 
we  get  HgoOjoNagSO^.  It  is  here  again  presumed  that,  whatever  the 
relation  of  II2O  is  to  HggOu,  the  same  will  hold  as  regards  Na2S04  in 
reference  to  10H2O.NaS2O4. 
Now,  referring  to  the  formula  of  acid  calcium  lactate,  it  will  be 
found  that  it  is  obtained,  in  the  same  manner  as  the  foregoing  com- 
pound, by  substituting  Ca  for      in  the  quadruple  group,  H^Lc^. 
The  empirical  or  molecular  formula  of  the  compound  formed  by 
dissolving  calcium  orthophosphate  in  lactic  acid  to  saturation  is 
Ca3(P04)2(IILc)4,  but,  on  the  principle  above  illustrated,  its  constitu- 
tional expression  is : 
(HLC2)— Ca— PO,— H 
cL 
(HLC2)— Ca— PO— H 
The  stable  lactophosphate,  Ca3(P04)2(HLc)g,  is  similarly  written,  as: 
(HLC2)— Ca— PO4— (H^Lc) 
c'a 
I 
(HLC2)— Ca— PO,— (H2LC) 
The  general  experience  with  the  four-molecule  lactophosphate  has 
uniformly  pointed  to  its  unstable  character,  nevertheless  the  Pharma- 
copoeia has  adopted  this  compound.  On  the  occasion  whereat  the 
writer  announced  its  instability  especial  reference  was  made  to  the  six- 
molecule  salt,  and  this  was  recommended  for  its  permanence  and  gen- 
eral desirability.  A  process  was  also  submitted  for  its  preparation, 
based  on  the  usual  method  for  making  the  four-molecule  salt.  It  was, 
however,  indicated  by  a  reaction,  reproduced  above,  that  it  could  be 
much  more  readily  obtained  by  an  inverse  operation  through  the  appli- 
cation of  calcium  lactate  and  phosphoric  acid.  The  writer,  however, 
did  not  give  a  process  based  on  this  principle,  firstly,  for  the  reason  that 
calcium  lactate  was  not  found  in  the  market,  but  chiefly  for  the  reason 
that  a  suitable  phosphoric  acid  was  equally  scarce.  Since,  however,  the 
Pharmacopoeia  now  directs  a  phosphoric  acid  of  proper  form  and  qua- 
lity, the  inverse  method  can  therefore  be  employed  with  great  advan- 
tage over  the  rather  tedious  and  circumstantial  official  process.  In 
39 
