320  Sodio-Bismuth  Citro-Pyroborate.  {Am^uT^8?4arm* 
readily  and  completely  decomposed  by  a  comparatively  small  quantity 
of  water.  In  its  production  in  the  solid  form  some  care  is  necessary, 
during  the  later  stage  of  the  evaporation,  not  to  let  the  temperature 
sink,  as  this  partial  cooling  in  contact  with  the  modicum  of  water 
causes  a  decomposition  and  consequent  turbidity  which  subsequent 
heating  does  not  correct. 
The  following  formula  yields  it  with  the  greatest  ease : 
Bismuth  citrate   399  parts. 
Sodium  pyroborate,  in  powder   382  44 
Water  sufficient. 
Mix  the  citrate  and  borax  with  2,400  parts  of  water  and  apply  heat 
until  the  citrate  is  all  dissolved.  Then  filter  the  solution  after  having 
diluted  it  with  its  volume  of  water  and  evaporate  it  at  a  uniform  tem- 
perature to  a  dense  syrupy  consistence  and  spread  it  on  plates  of  glass 
or  porcelain  so  that  on  cooling  the  salt  may  be  obtained  in  scales. 
The  writer  has  made  no  decisive  experiments  in  relation  to  the 
action  of  this  salt  on  solutions  of  pepsin.  When  a  solution  of  pep- 
sin prepared  with  chlorhydric  acid  is  first  carefully  neutralized  with 
sodium  bicarbonate  or  treated  with  a  slight  excess  of  borax  the  bismuth 
solution  produces  a  faint  flocculent  precipitate,  not  however  propor- 
tionate to  the  amount  of  pepsin  present.  The  character  of  the  precipi- 
tate was  not  ascertained.  Bismuth  citrate  also  forms  a  soluble  com- 
bination with  sodium  pyrophosphate,  but  the  writer  has  not  further 
examined  it. 
In  conclusion  it  may  be  said  that  when  borax  is  heated  with  bis- 
muthyl  nitrate  decomposition  ensues,  but  the  resulting  compound  is 
insoluble  in  excess  of  borax.  This  shows  that  a  sodio-bismuth  pyro- 
borate cannot  be  formed.  Some  time  since  the  writer  attempted  to 
prepare  bismuth  salicylate  by  heating  bismuthyl  nitrate  with  sodium 
salicylate.  Perfect  decomposition  could  not  be  attained,  and  the 
writer  then  heated  the  nitrate  with  salicylic  acid.  A  very 'surprising 
result  followed  this  experiment.  Combination  speedily  occurred  and 
a  readily  fusible  brown-red  crystalline  mass  was  formed.  Stronger 
acids  liberated  from  this  a  brown-red,  peculiarly  odorous  acid  which, 
without  further  examination,  appeared  to  be  one  or  more  of  the  three 
nitro-salicylic  acids.  This  result  is  in  so  far  remarkable  that  it  easily 
effects  the  generation  of  nitro-acids  which  ordinarily  can  only  be  pro- 
duced by  the  direct  intervention  of  very  concentrated  nitric  acid  at  a 
high  heat. 
