596 
Tri-Basic  Sodium  Phosphate. 
(Am.  Jour.  Pharm. 
X  December,  1902. 
resistant  properties  of  wood  treated  by  different  processes,  together 
with  physical  tests  upon  the  same,  is  now  under  investigation  by  a 
commission  appointed  by  the  Bureau  of  Building  Construction  of 
the  City  ot  New  York,  and  I  have  no  doubt  that  their  report  when 
published  will  throw  much  additional  light  upon  this  most  important 
subject. 
Philadelphia,  July,  1902. 
TRI-BASIC  SODIUM  PHOSPHATE. 
By  H.  B.  EigeIvBERNer. 
In  looking  through  a  number  of  chemical  text  and  reference 
books,  I  find  practically  no  mention  of  Tri-Basic  Sodium  Phosphate 
(Na3P04+l2H20). 
Inasmuch  as  the  consumption  in  this  country  alone  amounts  to 
between  three  and  five  million  pounds  yearly,  it  seems  to  the  writer 
that  the  subject  is  worthy  of  more  notice  than  has  previously  been 
accorded  it.  The  ingredients  of  this  manufacture  are :  sulphuric 
acid,  phosphate  rock,  soda  ash  and  caustic  soda. 
The  three  stages  of  the  operation  are  shown  by  the  following 
reactions : 
Ca3(P04)2-f3H2S04=3CaS04-f2H3P04. 
H3P04 + Na2C03=Na2HP04 + H20 + C02. 
Na2H  P04 + NaO  H =Na3P04  +  H20 . 
The  above  reactions  are  more  or  less  ideal,  and  no  account  is 
taken  of  the  minor  reactions  between  small  amounts  of  the  calcium 
acid  phosphate  and  the  phosphates  of  iron  and  alumina,  carbonates, 
eto 
The  details  of  its  crystallization  and  the  appearance  of  the  final 
product  are  very  similar  to  the  Jfamiliar  di-basic  sodium  phosphate 
(Na2HP04+ 1 2H20). 
Probably  one-half  the  T.S.P.  (tri  -  sodium  phosphate)  manufac- 
tured goes  into  the  different  boiler  compounds,  the  rationale  of  its 
use  being  to  convert  the  hardenable  carbonates  and  sulphates  of 
lime,  magnesium  and  other  incrusting  minerals  into  unhardenable 
phosphates  and  to  neutralize  the  acids  released  by  decomposition. 
'  3  (CaSO-4+2H20)  +  2(Na3P04+i2H20)=Ca3(P04)2+3(Na2S04-f 
I0H20).  A  corresponding  reaction  takes  place  in  the  carbonates — 
sodium  carbonate  in  solutions  and  calcium  phosphate  precipitated. 
