VARIETIES. 
469 
Preparation  of  Pure  White  Gutta  Percha. — This  substance  is  now 
much  used  in  dentistry  and  for  other  purposes,  and  as  different  qualities? 
some  of  them  very  inferior,  are  in  the  market,  some  of  our  professional 
readers  may  thank  us  for  the  details  of  a  simple  process  for  manufacturing 
it.  Four  ounces  of  the  purest  gutta  percha  that  can  be  selected  are  to  be 
digested  for  several  days  with  five  pounds  of  methyl-chloroform,  until  a 
solution  is  obtained  thin  enough  to  pass  through  filtering  paper,  care 
being  taken  during  the  operation  to  prevent  any  loss  of  the  chloroform 
by  using  the  apparatus  constructed  for  that  purpose.  The  solution  is 
then  to  be  filtered  (an  additional  pound  of  chloroform  will  facilitate  this), 
and  should  then  be  clear  and  nearly  colorless.  Alcohol  is  now  to  be 
added  in  sufficient  quantity  to  precipitate  the  gutta  percha  in  a  volumin- 
ous white^mass,  which  then  is  to  be  washed  with  alcohol,  pressed  in  a 
cloth  and  dried  in  the  air.  It  must  finally  be  boiled  in  water  in  a 
porcelain  vessel  for  half  an  hour,  and  while  still  hot  rolled  into  sticks. 
The  chloroform  can  be  separated  from  the  alcohol  by  adding  water,  and 
the  alcohol  recovered  by  distillation, — Journ.  of  Applied  Chemistry,  July 
1870. 
Cement  for  Knife  Handles. — The  best  cement  for  this  purpose  consists 
of  one  pound  of^colophony  (purchasable  at  the  druggists)  and  eight  ounces 
of  sulphur,  which  are  to  be  melted  together,  and  either  kept  in  bars  or 
reduced  to  powder.  One  part  of  the  powder  is  to  be  mixed  with  half 
a  part  of  iron  filings,  fine  sand  or  brick  dust,  and  the  cavity  of  the 
handle  is  then  to  be  filled  with  this  mixture.  The  stem  of  the  knife 
or  fork  is  then  to  be  heated  and  inserted  in  the  cavity,  and  when  cold  it 
will  be  found  fixed  to  its  place  with  great  tenacity. — Druggists'  Circidar. 
Black  Varnish  for  Iron-iuork.  Asphaltuni,  48  lbs.,  fuse  ;  add  boiled 
oil,  10  gallons,  red  lead  and  litharge,  of  each  7  lbs. ;  dried  and  powdered 
white  copperas,  3  lbs.  Boil  for  two  hours  ;  then  add  dark  gum  amber 
(fused),  8  lbs. ;  hot  linseed  oil,  2  gallons  ;  boil  for  two  hours  longer,  or  till 
a  little  of  the  mass,  when  cooled,  may  be  rolled  into  pills;  then  withdraw 
the  heat,  and  afterwards  thin  down  with  oil  of  turpentine,  30  gallons. 
Used  for  the  iron-work  of  carriages  and  for  other  nice  purposes. — Drug. 
Cir.  and  Chem.  Gaz.,  March,  1870,  from  Blinn's  Workshop  Companion. 
Experiments  on  the  Production  of  Sulphuric  Acid  from  Gypsum.  H. 
Reinsch.  a  quintal  (hundredweight)  of  gypsum,  CaCSOs'iHO,  con- 
tains about  57  lbs.  of  sulphuric  acid  (so-called  English).  The  author,  after 
referring  to  the  very  many  hitherto  unsuccessful  attempts  made  to  obtain 
this  acid  from  this  most  abundantly-found  mineral,  states  that,  when  he 
mixed  two  parts  of  pulverized  gypsum  with  one  part  of  carbonate  of  am- 
monia, and  poured  water  over  this  mixture,  complete  decomposition  of 
the  gypsum  ensues,  sulphate  of  ammonia  is  formed,  and  carbonate  of  lime. 
