\ 
200  UNGUENTUM  HYDRARGYRI. 
According  to  the  foregoing  experiments  and  results,  the  follow- 
ing may  be  set  down  as  the  constituents  of  Senna : — 
1.  A  resin,  soluble  in  alcohol  and  ether. 
2.  Gum. 
3.  A  brown  coloring  matter. 
4.  A  yellow  coloring  matter,  "  Chrysoretin." 
5.  Chlorophylle. 
6.  Vegetable  albuminous  matter. 
7.  Glucose. 
8.  A  neutral,  crystalline,  purgative  principle.  [Sennin.] 
9.  Lime. 
10.  Gallic,  and  citric  or  some  similar  vegetable  acids. 
UNGUENTUM  HYDRi  RGYRI. 
By  Gustavus  Pile. 
>  (An  Inaugural  Essay.) 
In  view  of  the  fact  that  many  preparations  of  Pharmacy  for- 
merly made  by  the  apothecary  are  now  furnished  by  the  manu- 
facturing chemist,  it  would  appear  but  reasonable  that  the  Phar- 
maceutist should  be  able,  approximately  at  least,  to  ascertain 
the  reliability  of  the  articles  he  may  purchase,  as  to  purity  and 
strength.  Accordingly,  tests  are  instituted,  either  mechanical 
or  chemical,  by  which  the  value  of  many  preparations  is  readily 
and  satisfactorily  determined. 
In  the  present  state  of  the  knowledge  of  Pharmaceutists 
generally,  the  more  simple  the  tests  the  better  :  complicated 
proceedings,  or  very  nice  arrangements  of  apparatus,  would 
deter  many  druggists  from  undertaking  the  operation  ;  and, 
although  the  analytic  chemist,  with  his  varied  apparatus  and  re- 
agents, would  give  more  satisfactory  results,  yet,  generally,  such 
accuracy  is  not  needed. 
The  writer,  in  casually  experimenting  with  a  lot  of  mercurial 
ointment,  in  order  to  ascertain  its  strength,  was  led  to  believe 
that  the  subject  would  prove  acceptable  for  a  thesis,  and  accord- 
ingly has  noted  down  some  observations  which  he  thinks  to  be 
not  generally  known. 
The  determination  of  the  relative  amount  of  mercury  present 
