AnMi?chj8oo.rm'}  Pharmaceutical  Meeting.  149 
MINUTES  OF  THE  PHARMACEUTICAL  MEETING. 
The  regular  monthly  Pharmaceutical  Meeting  was  held  Tuesday,  February 
20th,  with  Mr.  Richard  M.  Shoemaker,  a  member  of  the  College  and  a  mem- 
ber of  the  old-established  drug  firm  of  Robert  Shoemaker  &  Co.,  in  the  chair. 
The  first  speaker  on  the  programme  was  Prof.  Samuel  P.  Sadtler,  who  gave 
a  very  interesting  talk  on  "  Mineral  Tannage,"  illustrating  the  same  with  speci- 
mens. 
It  may  be  mentioned  here  that  Professor  Sadtler  has  been  employed  for  the 
past  seven  years  as  an  expert  in  litigation  concerning  tanning  processes  and  has 
in  that  connection  patented  two  processes  for  chrome  tanning. 
In  describing  the  skins  which  are  used  for  making  leather,  he  said  that  in 
ordinary  usage  the  skms  of  larger  animals  are  known  as  hides,  whereas  those 
of  smaller  animals  are  known  as  skins.  He  said  that  the  animal  skin,  owing 
to  the  processes  which  have  been  used  for  removing  the  hair  and  otherwise 
cleansing  it,  is  in  an  extremely  sensitive  condition  when  ready  for  tanning,  and 
if  exposed  to  high  temperature  soon  spoils,  or  if  dried  in  this  condition  it  be- 
comes like  parchment. 
Coming,  then,  to  consider  the  subject  of  tanning,  the  speaker  said  that 
chemists  differ  as  to  whether  the  process  involved  in  tanning  is  a  chemical  or  a 
mechanical  one.  A  number  of  methods  have  been  used  for  converting  animal 
skins  into  leather,  and  of  the  processes  now  in  use  that  of  tanning  by  the  use 
of  vegetable  extracts  or  infusions  containing  tannic  acid  was  the  earliest  known. 
In  this  process  the  tannin  combines  with  the  fibre  of  the  skin  so  that  it  does 
not  become  parchment-like  on  drying.  Later  it  was  discovered  that  certain 
mineral  salts  have  a  similar  effect  on  the  skins,  the  processes  involving  this 
action  being  grouped  under  the  head  of  mineral  tannage  or  tawing.  Still 
another  process  of  tanning  is  that  involving  the  application  of  oil  to  the  skins 
and  its  subsequent  oxidation. 
Alum  was  one  of  the  first  of  the  mineral  salts  to  be  used  for  tanning  pur- 
poses, but  is  found  to  be  distinctly  inferior  to  tannic  acid  in  this  respect,  owing 
to  the  fact  that,  when  the  leather  is  put  into  water,  the  alum  is  washed  out  and 
the  leather  becomes  parchment-like  on  drying.  Later  it  was  found  that  other 
oxides  like  those  of  iron  (F203)  an(I  chromium  (Cr203)  had  the  property  of  com- 
bining with  hide  fibre.  The  iron  salts  do  not  appear  to  be  very  satisfactory  in 
this  respect,  however,  as  the  leather  becomes  hard  and  brittle. 
For  our  earlier  knowledge  of  chrome  tanning  we  are  indebted  to  the  Ger- 
man chemists,  Knapp  and  Heinzerling.  The  chrome  tanning  industry  has, 
however,  assumed  the  greatest  proportions  in  this  country,  Philadelphia  being 
its  chief  centre,  and  in  recent  years  a  number  of  patents  have  been  taken  out 
for  various  modified  processes.  One  of  the  first  of  these  was  the  Schultz 
patent  process,  which,  though  slow  to  be  adopted  by  tanners,  has  proved  of 
great  value,  and  has  been  the  occasion  of  much  litigation  extending  from  1892 
to  the  present  time,  owing  to  the  number  of  infringements  of  the  patent. 
The  process,  briefly  stated,  is  (1)  to  treat  the  skins  with  a  solution  of  potassium 
bichromate  in  the  presence  of  acid,  which  liberates  chromic  acid  (Cr03)  ;  (2) 
then  to  put  them  into  a  bath  of  an  acidified  sulphite  or  hyposulphite  for  reduc- 
ing the  chromic  acid,  whereby  chromic  oxide  (Cr203)  is  produced.  The  chrome 
tanning  process  has  been  found  to  be  particularly  applicable  to  light  skins,  such 
