1 1 2  Basicity  of  the  Phosphorus  Acids.  {Am'ifc87h6ann' 
and  pyrophosphoric  acid,  (P207H4),  third  in  the  series.  But,  as  the 
first  and  second  members  differ  by  one  equivalent  of  hydroxyl,  (OH), 
the  second  and  third  would  vary  by  the  same  difference,  and  hence 
pyrophosphoric  acid  under  this  law  should  be  written  P05H4.  This 
does  not,  however,  agree  with  facts,  as  was  exhibited  by  the  com- 
parison just  preceding. 
By  the  new  arrangement  as  above  proposed,  which  in  reality  is  the 
natural  and  true  system  of  notation  for  the  phosphorus  acids,  being  in 
perfect  consonance  with  the  typal  theory,  all  the  phosphoric  acids  con- 
tain the  bivalent  radical  phosphoryl,  (P204)",  in  two  cases  in  combina- 
tion with  partially  affected  or  typoid  hydrogen  and  hydroxyl,  and  in  one 
wholly  in  union  with  hydroxyl.  The  affected  or  typoid  hydrogen, 
being  yet  distantly  influenced  by  the  phosphorus  of  the  radical,  does 
not  assume  the  function  of  hydroxyl,  and  therefore,  particularly  in  the 
case  of  orthophosphoric  acid,  it  ordinarily  possesses  no  salifying  power  \ 
consequently  this  affected  hydrogen  does  not  virtually  represent  basisity. 
It  is,  however,  replaceable  by  bases,  under  extraordinary  conditions  •> 
but  in  such  instances  the  highly  basic  character  of  the  compound 
barely  admits  of  classification  as  a  true  salt. 
Ignoring  the  indifferent  hydrogen,  it  will  then  be  seen  that  meta- 
phosphoric  acid  is  dibasic,  pyrophosphoric  acid  tribasic  and  orthophos- 
phoric acid  tetrabasic.  But,  admitting  the  full  value  of  the  hydrogen, 
then  metaphosphoric  acid  remains  dibasic,  pyrophosphoric  acid  be- 
comes tetrabasic,  and  orthophosphoric  hexabasic. 
For  convenience  sake,  they  may  be  represented  as  monobasic,  di- 
basic and  tribasic.  It  is,  however,  atomically  correct  that  they  be 
designated  as  bibasic,  tetrabasic  and  hexabasic,  in  which  case  the  tetra- 
basisity  of  pyrophosphoric  acid,  as  at  present  held,  would  be  correct, 
but  in  every  other  instance  it  would  be,  typically  considered,  utterly 
wrong. 
But  absolute  typic  value  is  the  perfect  index  of  basicity,  therefore 
typoid  hydrogen  is  not  admissible  in  a  determination  of  that  quality, 
and  as  various  indications  point  favorably  that  way,  it  appears  that  the 
correct  basic  value  of  the  phosphoric  acids  is  shown  by  the  new  ar- 
rangement, in  which  they  are  respectively  dibasic,  tribasic  and  tetra- 
basic, regardless  of  typoid  hydrogen. 
Although  fused  sodium  pyrophosphate  is  correctly  represented  by 
Na4  (P207),  it  appears  highly  probable  that  the  aqueous  solution  con- 
tains it  as  Na3H  (P207)  (NaOH.)    This  expression,  in  a  measure,  ex- 
