ANo4°mbe?S*}  Properties  and  Uses  of  Formaldehyde.  625 
This  illustrates  a  striking  peculiarity  in  the  antiseptic  action  of 
formaldehyde ;  for  whilst  it  exerts  an  intensely  powerful  inhibitory 
effect  on  bacteria  generally,  especially  those  of  putrefaction,  in  con- 
trast it  has  but  a  comparatively  feeble  influence  in  preventing  the 
development  of  the  lower  forms  of  plant  life.  Hence,  vegetable 
solutions  preserved  by  its  aid,  although  retaining  their  color  and 
other  physical  characters  to  a  remarkable  degree,  are  exceedingly 
prone  to  develop  mouldy  growths,  etc.,  and  if  this  is  to  be  avoided, 
the  proportion  of  antiseptic  must  be  increased  to  an  extent  far 
greater  than  required  to  simply  arrest  putrefactive  change. 
Meat,  fish,  etc.,  may  be  kept  for  several  days  during  the  hottest 
weather  by  placing  it  in  a  well-covered  dish  with  a  tuft  of  cotton- 
wool moistened  with  from  4  to  8  drops  of  solution  of  formaldehyde. 
The  antiseptic  vapor  does  not  communicate  the  slightest  odor  or 
taste  to  the  meat,  etc.,  and,  after  considerable  experience  of  this 
method,  I  have  never  found  it  fail  to  maintain  the  articles  absolutely 
untainted  for  four  or  five  days,  even  under  the  severest  conditions 
of  temperature. 
Disinfection  by  formaldehyde  vapor  generated  directly  from 
methylic  alcohol  has  lately  attracted  considerable  attention.  The 
simplest  form  of  apparatus  for  the  purpose  consists  of  an  ordinary 
spirit  lamp  provided  with  a  coil  or  spiral  of  platinum  extending 
about  I  inch  above  the  wick.  After  lighting  the  lamp  and  allowing 
the  platinum  to  become  red  hot,  the  flame  is  extinguished.  The 
platinum  continues  to  glow  in  contact  with  the  air  and  methylic 
alcohol  vapor,  and  the  latter  rising  from  the  wick  becomes  partially 
converted  into  formaldehyde,  the  action  being  maintained  as  long 
as  any  methyl  alcohol  remains  in  the  reservoir.  In  this  apparatus, 
a  large  proportion  of  the  alcohol  escapes  oxidation  and,  in  conse- 
quence, several  improved  forms  have  been  devised.  In  one,  resemb- 
ling a  plumber's  blow-lamp,  a  stream  of  methylic  alcohol  vapor  is 
directed  upon  incandescent  platinum  ;  there  are  also  air-holes, 
which  can  be  so  adjusted  as  to  regulate  the  proportions  of  air  and 
alcohol  vapor ;  in  this  lamp  the  greater  part  of  the  alcohol  is  con- 
verted. Formaldehyde  vapor  may  also  be  generated  in  an  apart- 
ment by  spraying  the  solution  into  the  atmosphere  or  heating  it  in 
an  evaporating  dish.  Diffusion,  however,  is  slow  in  the  latter  case, 
as  has  already  been  stated,  and  it  is  much  better  to  allow  the  solu- 
tion to  fall  drop  by  drop  on  a  heated  plate  of  metal.    A  bandy  ar- 
