308 
ON  LAPIS  CALAMINARIS. 
ON  LAPIS  CALAMINARIS. 
By  Ferris  Bringhurst,  Wilmington,  Del. 
{Extract  from  an  Inaugural  Thesis.') 
In  going  through  a  course  of  qualitative  analysis  last  winter, 
I  examined  a  specimen  of  calamine  obtained  from  a  wholesale 
druggist  of  this  city,  and  was  surprised  at  the  large  amount  of 
sulphate  of  baryta  it  contained,  and  the  small  yield  of  zinc,  of 
which  I  found  but  a  mere  trace.  This  induced  me  to  make  an 
investigation  of  the  matter,  the  result  of  which  is  given  in  this 
paper. 
In  the  U.  S.  Dispensatory,  mention  is  made  of  the  experi- 
ments of  Mr.  Brett,  who,  some  years  ago,  examined  the  calamine 
of  the  English  shops,  and  found  it  to  contain  from  78  to  87.5 
per  cent,  of  sulphate  of  baryta. 
According  to  the  Pharmacopoeia,  calamine  is  an  impure 
carbonate  of  zinc,  but  the  results  of  my  experiments  have  satis- 
fied me  that  zinc,  where  it  does  exist,  is  in  very  small  propor- 
tion, and  that  a  large  portion  of  the  lapis  calaminaris  of  our 
shops,  does  not  contain  even  a  trace  of  zinc. 
Analyses. — The  following  analyses  were  made  in  the  laboratory 
of  Dr.  F.  A.  Genth,  to  whom  the  author  is  much  indebted  for 
his  knowledge  of  chemistry,  obtained  there  during  the  past  two 
winters. 
The  last  three  analyses,  though  not  so  complete  as  the  first 
three,  are  sufficiently  so  to  answer  the  object  of  the  investigation. 
No.  1,  was  a  sample  of  calamine  from  a  retail  druggist  in  this 
city.  Its  color  was  a  light  shade  of  peach-blossom.  Before  the 
blowpipe  on  charcoal  it  gave  a  faint  yellow  incrustation,  and  the 
fused  mass,  when  moistened,  blackened  silver,  evincing  the 
presence  of  sulphur. 
Specific  gravity  3.88. 
Loss  by  ignition, 
Sesquioxide  of  Iron, 
Lime, 
Baryta,  . 
Oxide  of  Lead, 
Silica,  . 
Carbonic  Acid, 
Sulphuric  Acid, 
Fe203 
CaO 
BaO 
PbO 
Si03 
co2 
so3 
Pr.  ct. 
.50 
1.50 
2.76 
51.55 
a  trace 
16.50 
a  trace 
26.95 
99.76 
