Am.  Jour.  Pharm,  ] 
Sept.  1,1871.  J 
Varieties. 
421 
Cold  may  possibly  have  had  some  part  in  this  diminution  of  volume  ;  but  the 
temperature  necessary  to  produce  so  great  a  reduction  in  volume  must  have 
reached — 214P  0.  at  the  point  where  the  hail  was  formed— if  cold  had  been  the 
only  cause  in  play.  Whatever  explanation  we  assign  to  this  interesting  obser- 
vation, it  must  certaiYily  be  regarded  as  the  most  unexpected  one  which  has 
yet  appeared  in  the  study  of  this  puzzling  phenomenon.  Prof.  R.  recommends, 
the  diligent  use  of  the  microscope  as  the  only  means  of  solving  the  problem  of 
the  history  of  hail. — Journ.  Frankl.  Inst.,  August,  1871. 
"  Waterproof  Glue. — Ordinary  glue  can  be  rendered  insoluble  in  water  by 
adding  to  the  water,  with  which  it  is  mixed  when  required  for  use,  a  small 
quantity  of  bichromate  of  potash,  and  exposing  the  articles  to  which  it  is  ap- 
plied to  the  light.  Chromic  acid  has  the  property  of  rendering  glue  and  gela- 
tin insoluble,  and,  as  the  operation  of  heating  the  glue-pot  is  usually  conducted 
in  the  light,  no  special  exposure  of  the  articles  to  which  it  is  attached  need  be 
made.  It  is  probable  that  paper  could  be  rendered  impervious  to  water  by 
pasting  the  sheets  with  this  prepared  glue.  The  bichromate  is  said  to  render 
rubber  particularly  hard  and  unattackable  by  hot  water.  The  chromated 
gelatin  ought  also  to  be  tried  on  parchment  paper,  wood,  leather,  and  cloth 
fabrics.  The  proportion  of  bichromate  to  be  taken  must  be  ascertained  by  ex- 
periment; for  most  purposes  one-fiftieth  of  the  amount  of  glue  employed  will 
be  found  to  suffice, — that  is,  one  pound  of  dry  bichromate  of  potash  to  fifty 
pounds  of  dry  glue. 
"  Many  applications  of  waterproof  glue  will  readily  suggest  themselves  to 
our  readers.  The  Albert  photographic  process  is  founded  upon  this  property 
of  gelatin,  and  billiards-balls,  buttons,  and  ornaments  are  now  largely  made  of 
chromated  glue." — Dental  Cosmos,  August,  1871,  from  Sci.  Amer. 
Liquid  Glues. — F.  L.  J.,  of  Ark.,  states  [Ibid.)  that  an  excellent  liquid  glue 
can  be  made  by  dissolving  glue  in  nitric  ether.  The  ether  will  only  dissolve  a 
certain  amount  of  the  glue  ;  consequently  there  need  be  no  fears  of  making  the 
solution  too  thick.  The  glue  thus  made  is  about  the  consistency  of  molasses, 
and  is  doubly  as  tenacious  as  that  made  with  hot  water.  If  a  few  bits  of  india- 
rubber,  cut  into  scraps  the  size  of  a  buckshot,  be  added,  and  the  solution  al- 
lowed to  stand  a  few  days,  being  stirred  frequently,  it  will  be  all  the  better, 
and  will  resist  dampness  twice  as  well  as  glue  made  v^-ith  water.  The  best 
liquid  glue  that  I  have  any  knowledge  of  is  made  as  follows :  take  of  gum  shel- 
lac, three  parts  ;  caoutchouc  (india-rubber),  one  part,  by  weight.  Dissolve  the 
caoutchouc  and  shellac,  in  separate  vessels,  in  ether  free  from  alcohol,  applying 
a  gentle  heat.  When  thoroughly  dissolved,  mix  the  two  solutions,  and  keep 
in  a  bottle  tightly  stoppered.  This  glue  is  called  marine  glue,  and  resists  the 
action  of  water,  both  hot  and  cold,  and  most  of  the  acids  and  alkalies.  Pieces 
of  wood,  leather,  or  other  substances,  joined  together  by  it,  will  part  at  any 
other  point  than  at  the  joint  thus  made.  If  the  glue  be  thinned  by  the  ad- 
mixture of  ether,  and  applied  as  a  varnish  to  leather  along  the  seams  where  it 
is  sewed  together,  it  renders  the  joint  or  seam  water-tight,  and  almost  impossi- 
