540  On  Citric  Acid,  Etc.  {^%iVXm'^''' 
The  analysis  of  the  salt  in  scales  was  conducted  in  this  wise  : 
2-302  grm.  of  the  ammonia-citrate  of  bismuth  in  scales  were  dissolved 
in  a  little  warm  water,  and  a  small  piece  of  blue  litmus  paper  made 
to  float  on  the  liquid.  The  paper  turned  red  immediately.  Then 
the  same  filtered  solution  of  ammonia  already  mentioned  was  added 
carefully  till  saturation  ;  twenty-five  measures  were  necessary,  which 
corresponds  to  one-half  equivalent.  This  demonstrated  already  that 
the  quantity  of  ammonia  contained  in  the  salt  was  IJ  equivalent. 
The  liquid  was  then  decomposed  by  caustic  potassa  in  excess,  with 
the  help  of  a  moderate  heat,  etc.,  precisely  in  the  manner  described 
for  the  analysis  of  citrate  of  bismuth.  The  following  numbers  were 
obtained  :    Teroxide  of  Bismuth  1-170,  Citric  Acid  0-823. 
The  proportion  of  ammonia  being  already  known,  the  compound 
may  be  reconstructed  thus  : 
Teroxide  of  Bismuth    1-170  =  1  equivalent 
Citric  Acid  0-823     1  " 
Ammonia  0-122  =  1^ 
Water  0-180 
Loss  0-007 
2-302 
Or  in  chemical  symbols  :  IJ  N  H3,  BiOg.  C,^      0,^+4  HO  =  460-4. 
I  must  say  that  in  this  salt  I  believe  the  proportion  of  ammonia 
may  vary  slightly,  according  to  the  mode  of  evaporation  ;  this  pro- 
portion, however,  cannot  fall  below  IJ  equivalent  without  causing  a 
decomposition  of  the  salt. 
ANALYSIS  OF  THE  DOUBLE  CITRATES  OF  BISMUTH  AND  POTASSA,  SODA 
AND  LITHIA. 
I  believe  these  combinations  have  never  been  mentioned  nor  ob- 
tained yet  by  anybody.  Yet,  besides  their  interest  in  a  chemical 
point  of  view,  I  think  they  Avill  become  of  some  importance  to  the 
medical  profession,  on  account  of  their  greater  stability  than  the  cor- 
responding ammonia  salt.  For  instance,  a  solution  of  citrate  of  bis- 
muth and  soda  may  be  kept  for  weeks  in  warm  weather  without  the 
addition  of  alcohol ;  the  only  change  observable  is  the  mouldiness 
common  to  all  the  diluted  solutions  of  citrates,  while  a  solution  of 
citrate  of  bismuth  and  ammonia  by  the  side  of  it  is  decomposed  in 
twenty-four  hours,  letting  the  ammonia  escape  and  forming  a  heavy 
insoluble  sediment  which  contains  almost  all  the  bismuth. 
