White  Crayons.  Pure  white  chalk
is  cut  into  crayons,  or  they  are  made
from  white  lead,  zinc  white,  or  zino
oxide  stirred  into  a  dough  witn  milk.
Pencils  for  WrUdng  Upon  Glass,
Melt  in  a  saucer :

Spermaceti 4  parts.
Tallow S    ••    ■

Wax 2    "

Add  to  this,  with  constant  stirring*:

Bed  lead 6  parts.
Potash 1  part.
Contihue  to  heat  the  mass  for  half  an
hour  and  then  pour  i^  into  small  p^lass
tubes  the  size  or  a  lead-pencil.  When
the  compound  has  become  cold  it  is
forced  into  small  wooden  tubes  and
sharpened  with  a  knife.
Pencils  for  Marking  Linen.  Ei^ht
parts  of  alumina  are  thoroughly  dried
and  mixed  with  2  parts  of  very  finely
powdered  pyrolusite.  Add  to  these  a
solution  of  3  parts  of  nitrate  of  silver  in
5  of  distilled  water,  and  mix  the  mass
intimately  by  rubbing  and  kneading.
Pencils  are  rormed  from  this  mass  and
dried,  and  used  for  marking  liueu.
either  in  this  form  or  enclosed  in  wood
like  a  pencil.
The  alumina  is  prepared  by  precip-
itating a  solution  of  alum  with  ammo-
nia. But  pure  clay  may  also  be  used
instead  of  alumina.
Marking  Ink  for  Linen.  To  use  this
ink  it  is  necessary  to  soak  the  linen
with  a  finid  consisting  of  1  part  of
sodium  hy  pophosphite,  2  of  gum  Arabic,
and  16  of  distilled  water.  When  the
linen  is  dry  it  is  smoothed  and  marked
with  an  ink  consisting  of  1  part  of  silver


80


TECHNO-CHEMICAL  RECEIPT  BOOK.
nitrate,  6  of  gum  mucilage,  and  6  of
distilled  water.
