ARSENIURETTED  ALCOHOL  AS  A  PRESERVATIVE. 
245 
ON  THE  EMPLOYMENT  OF  ARSENIURETTED  ALCOHOL  FOR  THE 
PRESERVATION  OF  OBJECTS  OF  NATURAL  HISTORY,  ESPE- 
CIALLY INSECTS. 
By  M.  Leprieur. 
At  the  ordinary  temperature  pour  500  grammes  of  rectified 
alcohol,  weighing  at  94  per  cent.,  on  an  excess  of  opaque  arseni- 
ous  acid.  After  eight  hours  of  contact,  during  which  time  the 
liquid  is  frequently  shaken,  the  alcohol  is  filtered.  Upon  evapo- 
rating 200  grammes  of  the  solution  in  a  platinum  capsule  over 
a  water-bath,  a  residue  is  left  weighing  00-3  grammes,  or  0-15 
grammes  per  kilogramme.  On  employing  alcohol  at  85  per 
cent,  a  residue  is  left  of  0-102  grammes,  or  0*51  grammes  per 
kilogramme.  If  the  alcohol  at  85,  and  the  arsenious  acid,  are 
kept  in  contact  for  four  months,  the  residue  weighs  1-38  gram- 
mes per  kilogramme. 
To  be  as  energetic  and  complete  as  possible,  the  action  of  the 
arseniuretted  alcohol  should  take  place  on  tissues  very  recently 
deprived  of  life  ;  it  is,  consequently  indispensable  in  the  case  of 
insects,  for  example,  that  they  should  be  immersed  in  it  whilst 
still  alive,  or,  better  still,  after  having  been  asphyxiated  with 
the  vapor  of  ether,  chloroform,  or  benzole.  Some  of  them,  in- 
deed, must  not  be  immersed  living  in  even  pure  alcohol,  for  as 
soon  as  they  touch  the  liquid  they  open  their  elytra  and  spread 
their  wings  as  if  they  wished  to  fly  away. 
Almost  all  the  coleoptera,  the  hemiptera,  and  even  the  orthop- 
tera,  can  be  plunged  without  danger  into  the  arseniuretted 
alcohol,  provided  they  are  not  left  in  longer  than  ten  or  twelve 
hours  ;  after  this  time  they  must  be  taken  out  of  the  alcohol  and 
thrown  upon  blotting  paper,  then  they  are  to  be  pricked  or 
cemented  down  until  they  have  lost  by  evaporation  the  greater 
part  of  the  liquid. 
When  the  insects  have  been  allowed  to  dry  before  being 
plunged  into  arseniuretted  alcohol,  the  action  of  the  latter  is 
not  so  efficacious  ;  when  a  collection  is  much  attacked  by  larva, 
recourse  must  be  had  to  an  immersion  for  twelve  hours. 
Of  all  the  methods  which  have  been  proposed  to  preserve 
collections,  this  is,  according  to  M.  Leprieur,  the  best.    He  has 
