SOLUBILITY  OF  GLUE  IN  GLYCERIN. 
515 
SOLUBILITY  OF  GLUE  IN  GLYCERIN. 
By  John  M.  Maisch. 
Read  before  the  Philadelphia  College  of  Pharmacy,  Sept.  18,  1870. 
Having  recently  been  called  upon  as  expert  to  testify  in  a  suit 
involving  the  right  to  manufacture  a  composition  for  printing 
rollers  in  which  sugar  is  wholly  or  partially  substituted  by  gly- 
cerin, a  question  propounded  to  me  has  led  me  to  make  some 
experiments,  which  appear  to  possess  some  interest  to  pharma- 
cists and  to  point  to  a  valuable  improvement  applicable  for  tech- 
nical analysis.  The  facts  of  the  case,  leaving  the  legal  techni- 
calities out  of  the  question,  are  as  follows  :  A  patent  was  granted 
in  England,  on  Nov.  24,  1854,  to  Thomas  De  la  Rue,  for  a  com- 
position of  printing  rollers,  &c.,  consisting  of  glue  and  glycerin. 
In  this  patent  the  glue  is  made  by  macerating  so-called  glue 
pieces,  that  is,  cuttings  of  hides,  skins,  &c.,  in  water  for  several 
days,  after  which  they  are  dissolved  in  glycerin  with  the  aid  of 
heat.  This  process  may  be  shortened  by  substituting  glue  for 
the  glue  pieces,  and  dissolving  it  in  the  glycerin.  Subsequently 
a  patent  was  taken  out  in  the  United  States  for  similar  purposes, 
the  material  used  being  glue,  glycerin  and  sugar.  A  firm  of 
this  city  having  for  some  time  manufactured  such  a  mixture,  a 
suit  was  instituted  by  the  patentees  in  this  country  to  restrain 
the  Philadelphia  firm  from  continuing  the  manufacture  of  mate- 
rial for  printing  rollers  with  glycerin  as  an  ingredient. 
It  is  well  known  that  glue,  and  gelatin  in  general,  swells  up 
considerably  when  kept  in  cold  water  ;  it  absorbs  water  and 
loses  its  transparency,  and  then  dissolves  very  readily  in  hot 
water,  while  the  solution  is  effected  slowly  if  the  glue  is  at  once 
boiled  with  water  without  previous  maceration,  or  soaking  as  it 
is  technically  termed.  This  behavior  is  so  well  understood  that, 
even  in  the  kitchen,  the  gelatin  is  allowed  to  soften  in  cold 
water  before  it  is  boiled  to  form  a  jelly. 
It  is  also  well  known  that  glycerin  is  an  excellent  solvent, 
capable  to  dissolve  perhaps  all  compounds  which  are  soluble  in 
water,  or  in  water  and  alcohol,  and  many  which  are  soluble  in 
alcohol  but  not  or  merely  sparingly  in  water.  If  this  is  borne 
in  mind,  there  is,  even  at  first  sight,  nothing  improbable  or  un- 
