354 
METHOD  OF  OBTAINING  GLUE  FROM  LEATHER. 
these  circumstances,  loses  much  of  its  flexibility ;  hence  the 
quantity  of  glue  obtained  from  old  boots  and  shoes  is  very  in- 
considerable. 
As  I  thought  it  not  improbable  that  the  animal  portion  of  the 
leather  might  have  undergone  decomposition  by  losing  a  portion 
of  its  nitrogen,  various  kinds  of  leather  were  subjected  to  ultimate 
analysis,  but,  as  will  be  seen  from  the  subjoined  results,  the 
leather  appeared  to  have  merely  undergone  a  metamorphosis  by 
a  new  arrangement  of  its  molecules  without  any  of  its  nitrogen 
being  eliminated. 
New  Thick—    I.  0.185  gramme  gave  0.346  C02, 0.099  HO,  and  0.002  ash 
0.152      do.     do.  0.102  Pt. 
II.  0.255      do.     do.  0.475  C02, 0.130  HO,  and  0.0025  ash 
New  Thin—     I.  0.056  gramme  gave  0.098  C02  0.028  HO,  and 0.0015 ash 
0.012      do.     do.  0.059  Pt. 
II.  0.075      do.      do.  0.132  C02  0.035  HO,  and  0.002  ash 
0.198      do.     do.  0.113  Pt. 
Old  Thin—      I.  0.115  gramme  gave  0.21   C02,  0.06  HO,  and  0.002  ash 
0.241      do.     do.  0.154  Pt. 
II.  0,1725     do.     do.  0.315  C02  0.085  HO,  and  0.0025  ash 
0.195      do.     do.  0.123  Pt. 
NEW  THICK. 
NEW  THIN. 
OLD  THIN. 
L 
n. 
Mean. 
I. 
II. 
Mean. 
I. 
II. 
Mean 
50.81 
50.58 
46.61 
48.00 
49.73 
49.79 
5.94 
5.64 
5.53 
5.17 
5.21 
5.15 
9.52 
9.21 
8.25 
8.12 
9.12 
9.00 
Ash  
1.08 
1.00 
2.67 
2.66 
1.73 
1.75 
Though  the  decompositon  of  leather  under  pressure  by  lime  is 
no  doubt  interesting  in  a  scientific  point  of  view,  I  fear  it  is  not 
likely  to  be  an  economical  process,  as  even  the  thinner  kinds  of 
leather  have  a  considerable  value,  being  worth  about  twopence 
per  pound. 
In  conclusion,  I  may  remark,  that  the  only  practical  improve- 
ment of  importance  which  has  been  made  upon  the  process  of 
tanning  for  many  years,  is  that  which  is  technically  called 
"  handling  "  the  hides.  This  consists  in  frequently  withdrawing 
the  hides  from  the  tan-pit,  and  allowing  them  to  get  partially 
dried  ;  in  this  way  the  exhausted  solutions  of  tan  are  in  a  great 
