552  Blunder  in  Medical  Chemistry.  {^NovSbwjS? 
more  brain-work  the  more  of  that  element  is  excreted.  Therefore, 
to  restore  brain  waste,  give  phosphorus  pills."  Such  a  crudity  as 
this  would  be  scouted,  even  as  regards  the  mineral  kingdom,  e.  g.> 
in  the  simple — or  comparatively  simple — operations  of  metal- 
lurgy. 
In  the  second  place,  the  question  of  quantity  may  be  considered. 
As  a  bottle  of  lithia  water  contains  about  five  grains  of  lithia,  it  is 
chemically  equivalent  to  about  ten  grains  of  soda. 
The  quantity  of  blood  in  an  adult  being  about  100,000  grains, 
and  containing  about  294  grains  of  chloride  of  sodium,  equivalent 
to  about  156  grains  of  soda,  it  would  evidently  require  fifteen  or 
sixteen  bottles  of  lithia  water  to  replace  the  soda  by  lithia,  suppos- 
ing that  sodium  salts  were  absent  from  the  food. 
From  the  quantity  and  composition  of  the  urine,  however,  we 
know  that  about  140  grains  of  common  salt,  equivalent  to  about 
seventy-five  grains  of  soda,  are  excreted  every  twenty-four  hours, 
derived,  of  course,  from  the  food.  It  follows,  therefore,  that  from 
seven  to  eight  bottles  of  lithia  water  would  be  required  every  day 
for  the  sole  purpose  of  dealing  with  the  sodium  salts  introduced  in 
the  food. 
These  results  are  conclusive  as  to  the  value  of  the  present  prac- 
tice. 
To  the  chemist,  however,  the  above  figures  are  superfluous.  He 
knows  that  the  tendency  is  towards  the  formation  of  the  more  in- 
soluble, not  of  the  more  soluble,  compounds;  and  that  for  lithia  to 
be  of  any  service  in  avoiding  deposition  of  urates  in  the  joints  or 
bladder,  all  bases  which  form  compounds  with  uric  acid  of  less 
solubility  than  lithic  urate  (potassium,  sodium,  ammonium)  must  be 
absent. 
If  we  have  a  solution  containing  a  phosphate,  a  magnesium  salt 
and  free  ammonia,  we  know  that  in  a  longer  or  shorter  time  a  pre- 
cipitate of  ammonio^magnesic  phosphate  will  take  place,  and  the 
only  way  to  prevent  it  is  to  ensure  the  absence  of  one  of  the  con- 
stituents of  the  precipitate.  We  cannot  argue  "  phosphate  of 
potassium  is  more  soluble  than  ammonio-magnesic  phosphate,  so  by 
adding  a  salt  of  potassium  to  the  solution  we  shall  prevent  the 
formation  of  the  very  sparingly  soluble  magnesium  compound,"  and 
yet  that  is  the  assumption  with  regard  to  the  medicinal  use  of  lithia 
water. 
