346  PREPARATIONS  OF  ARSENIC. 
lenger's  mineral  solution.  It  was  a  solution  of  1|  grain  of  ar- 
senious  acid  with  a  little  hydrochloric  acid  in  one  ounce  of  water. 
This  and  the  preceding  preparation  constituted  the  only  com- 
pounds of  arsenic  ordered  in  the  London  Pharmacopoeia.  Being 
both  in  the  liquid  form,  it  was  to  be  regretted  that  they  were  not 
of  the  same  strength. 
Among  the  preparations  not  contained  in  the  Pharmacopoeia, 
there  were — 
Liquor  Sodce  Arseniatis  (Pearson's  Solution,)  and  Liquor 
Ammonia*  Arseniatis.  These  were  solutions  of  either  salt,  in 
the  proportion  of  four  grains  to  the  ounce ;  being  the  same  rel- 
ative strength  as  the  Liquor  Potassse  Arsenitis,  over  which  it 
was  questionable  whether  they  possessed  any  advantage. 
Arsenici  lodidum,  or,  as  it  was  sometimes  called,  Arsenici 
Teriodidum,  was  ordered  in  foreign  Pharmacopoeias,  where  in- 
structions, not  all  alike,  were  given  for  its  preparation.  This 
compound  was  sometimes  used  in  this  country,  although  not  re- 
cognized in  our  Pharmacopoeias.  A  solution  of  two  grains  to  an 
ounce  of  water  was  found  to  keep  without  change,  but  in  a 
stronger  solution  a  precipitate  formed.  The  author  stated  that 
he  had  tried  both  glycerine  and  sugar  for  preventing  the  decom- 
position and  precipitation  which  occurs  in  the  stronger  solution, 
and  found  sugar  to  succeed  better  than  glycerine.  He  had  also 
obtained  a  similar  result  with  iodide  of  iron. 
Liquor  Arsenici  et  Hydrargyri  Hydriodatis,  or,  as  it  was 
sometimes  called,  Donovan  s  Solution,  had  been  used  to  some  ex- 
tent, and  a  formula  for  it  was  now  given  in  the  Dublin  Pharma- 
copoeia. Several  modifications  in  the  process  for  its  preparation 
had  been  suggested  since  it  was  first  introduced  by  Mr.  Donovan. 
The  most  simple  process  was  that  of  the  United  States  Pharma- 
macopoeia,  where  iodide  of  arsenic  and  red  iodide  of  mercury 
were  directed  to  be  rubbed  together  with  water,  and  the  solution 
completed  by  the  application  of  heat. 
Quince  Arsenias,  and  other  compounds  of  quinine  and  arsenic, 
were  sometimes  ordered  in  medicine,  but  there  were  no  formulae 
for  their  preparation  in  any  of  the  Pharmacopoeias. 
Ferri  Arsenias,  obtained  in  the  form  of  a  dirty  green  precip- 
itate, on  adding  arseniate  of  soda  to  sulphate  of  iron,  was  the 
last  of  these  preparations  to  which  he  would  refer. 
