230 
Notes  o?i  Specific  Gravity. 
f  Am.  .lour.  Pharm. 
I       May,  1902. 
time,  and  they  can,  of  course,  be  used  wet  as  well  as  dry.  It  is 
important  that  it  is  kept  clean.  If  it  is  soiled,  the  best  method  of 
cleaning  is  by  washing  with  soap  and  water.  A  liberal  supply  of 
soap  is  always  beneficial  to  the  skin. 
The  best  method  to  prevent  shrinking  is  to  rinse  it  in  soap  suds 
before  drying.  When  dry,  rubbing  and  stretching  will  return  it  to 
its  former  softness. 
Chamois  skins  are  often  abused  through  ignorance  or  inexperi- 
ence. The  writer  has  seen  skins  that  were  returned  to  the  seller, 
who  in  turn  returned  them  to  the  manufacturer,  that  were  partly 
burned  into  charcoal,  evidently  caused  by  drying  in  strong  heat, 
likely  in  a  hot  oven,  others  shrunk  to  one-fourth  their  natural  size 
by  being  boiled  or  steeped  in  hot  water. 
It  should  be  remembered  that  a  chamois  is  gelatinous  animal  sub- 
stance, a  sort  of  oleate  of  gelatine,  and  too  much  heat  should  be 
avoided. 
NOTES  ON  SPECIFIC  GRAVITY. 
By  Thomas  S.  Wiegand. 
The  paper  of  Dr.  Hatcher,  in  a  recent  number  of  the  American 
Journal  of  Pharmacy,  has  called  my  attention  to  the  subject  of 
"  Specific  Gravity,"  and  as  the  importance  of  a  clear  understanding 
of  the  subject  is  of  such  great  advantage  to  the  pharmacist,  I  feel  no 
further  apology  is  necessary  for  calling  attention  of  members  to  the 
matter.  Dr.  Squibb,  at  the  meeting  of  the  American  Pharmaceuti- 
cal Association  held  in  Chicago,  in  1869,  in  a  report  on  the  Phar- 
macopoeia, shows  how  valuable  accurate  determinations  of  specific 
gravity  are  in  determining  the  quality  of  many  of  the  preparations 
of  the  Pharmacopoeia,  and  gives  a  discription  of  an  improved 
specific-gravity  bottle,  by  which  the  most  common  errors  in  ascer- 
taining specific  gravity  of  liquids  can  be  reduced  to  a  minimum  ;  but 
it  must  be  borne  in  mind  that  all  the  ordinary  weighings  are 
approximate  only  unless  the  absolute  weight  of  the  bottle  is  taken, 
for  all  the  usual  weighings  are  made  in  the  air  and  not  in  vacuo, 
and  the  bottle  which  contains  one  litre  of  water  will  hold  17- 7 
grains  of  air  and,  of  course,  there  is  this  much  less  weight  to  be 
used  as  a  counterpoise  when  the  bottle  is  being  used  in  taking  the 
specific  gravity  of  any  liquid  ;  then  the  temperature  at  which  the 
