*S^?;S^ }      Tlie  Cohesion-Figure*  of  Oils,  etc.  409 
moments  unites  ihto  a  thin  film.  The  spray,  as  it  spreads,  draws  out 
the  inner  portion  into  radiate  points,  which  open  into  a  beautiful  net- 
work, the  centre  cohering  closely. 
Croton  oil  throws  out,  in  spreading,  a  fine  spray  in  advance  of  the 
more  closely  cohering  portion,  which  follows  quickly.  The  outer  edge 
breaks  up  unevenly  into  little  indentations,  the  border  of  the  inside 
portion  being  quite  broken,  but  gradually  becomes  nearly  entire* 
The  surface  too  has  openings,  which  increase  quite  rapidly  in  size,  the 
outer  ones  being  much  the  larger.  In  the  final  breaking  up,  before  the 
holes  open  one  into  another,  the  outlines  are  beautifully  fringed. 
I  experimented  with  the  varieties  of  olive  oil,  alone,  and  with 
mixtures  of  the  varieties,  and  with  the  addition  of  other  oils  ;  but  I 
did  not  get  the  perfectly  formed  figures  in  so  short  a  time  as  Dr. 
Moffat  mentions.*  My  material,  probably,  had  either  been  adulter- 
ated, or  was  not  fresh,  which  last,  I  think,  would  make  quite  a  differ- 
ence. However,  with  each  variety  and  mixture  the  figure  was  dif- 
ferent. If  the  impurities  were  the  same  that  Dr.  Moffat  used,  it 
appears  that  differences  in  proportion  are  capable  of  detection. 
Indeed,  in  several  instances,  I  decided  that  an  approximate  calcula- 
tion of  the  amount  of  adulteration  is  quite  satisfactorily  shown  by 
the  figures  formed. 
Of  many  of  the  fixed-oil  figures  I  obtained  very  nice  patterns  by 
Dr.  Moffat's  method — dropping  thin  glazed  paper  upon  the  perfectly 
formed  figure,  for  an  instant,  then  pressing  between  blotting  paper  to- 
absorb  the  surplus  oil ;  or,  to  bring  out  the  pattern  more  clearly  7 
floating  the  paper  upon  a  colored  liquid  for  a  moment  or  two  before 
pressing. 
No  written  description  can  give  any  idea  of  the  beauty  of  these 
figures,  many  of  the  formations  being  very  delicately  and  peculiarly 
marked  ;  while  more  beautiful  than  the  form,  and  often  equally  char- 
acteristic is  the  exquisite  play  of  colors  upon  the  surface. 
University  of  Michigan,  July,  1874. 
COMMERCIAL  MERCURIAL  OINTMENT. 
By  Jacob  A.  Muthersbough,  Ph.  G-. 
Extracted  from  an  Inaugural  Essay. 
In  consideration  of  the  varying  strength  of  the  mercurial  ointment 
as  found  in  the  market,  I  thought  that  it  might  be  of  some  interest  to» 
*  Chem.  News,  XVIII,  No.  473. 
