before
starting:
Pounds.
Caustic soda 4
White arsenic 10
Sal-soda crystals 10

There should be also some means for heating the solution in case, as
sometimes happens because of impure materials, lack of skill, or some
unforeseen circumstance, the heat created by mixing the materials should be
insufficient to dissolve all the arsenic.

In a 5-gallon kettle or metal[9] pail place the 4 pounds of caustic soda,
add 1 gallon of cold water, and stir with a stick until the caustic soda is
practically all dissolved. Without delay begin adding the white arsenic, in
portions of a pound or two at a time, as fast as it can be dissolved
without causing the solution to boil, stirring all the time. If the liquid
begins to boil, stop stirring and let it cool slightly before adding more
arsenic. The secret of success is to work the arsenic in fast enough to
keep the solution very hot--nearly but not quite at the boiling point. The
result should be a clear solution, except for dirt. If the liquid
persistently remains muddy or milky, it may be because the operation has
been conducted so fast that much water has been boiled out and sodium
arsenite is beginning to crystallize, so add another gallon of water and
stir. If the solution does not then clear up, the caustic soda must have
been very low grade, and the undissolved substance must be arsenic. In that
case, put the kettle over the fire, heat nearly, but not quite, to boiling,
and stir. As soon as the solution of arsenic is complete, dilute to about 4
gallons, add the sodium carbonate, and stir until dissolved.

_Cautions._--It is necessary to avoid splashing. Hence never work
hurriedly; stir deliberately and regularly; do not dump in the arsenic and
sal soda, but carefully slide them in from a grocer's scoop held close to
the side of the pail and to the surface of the liquid. Perform the whole
operation in a well-ventilated place and avoid inhaling steam.

After the solution has become cold add water to make it to exactly 5
gallons,[10] mix well, let settle, and draw off into containers which can
be tightly corked or otherwise closed. Jugs or demijohns are best, but tin
cans will serve if occasionally inspected for leaks which may occur after a
time through the action of the solution upon the solder of the can.

Tar stock is prepared thus: In a large metal pail dissolve three-fourths of
a pound of caustic soda in 1 quart of wa