To Purify Water.--Filter the water well, and then add about three drops
of nitric acid to the pint. This can be used as absolutely pure water,
but I would recommend the use of distilled water as preferable.

Cleaning Mercury.--Make a small bag of chamois skin,
pour in the mercury, and squeeze it through the leather.
Repeat this several times, and filter by means of a funnel made
of paper, with a very small aperture, through which it will escape
and leave the particles of dust, or other substances, in the paper.
A paper with a pinhole through it will answer as well,
and it is less difficult to make.

Adhesive Paper.--Take gum arabic, four ounces, put it
in a wide-mouthed bottle and pour on water about one-third
above the gum. Add half ounce of isinglass, or fish glue,
and a small piece of loaf sugar. Let all dissolve, and spread
over French letter paper, with a brush or piece of sponge.
If once spreading is not enough, perform the same operation
a second time.

Black Stain for Apparatus.--Dissolve gum shellac in alcohol,
or procure shellac varnish at the druggists', stir in lampblack,
and apply with a sponge or bit of rag. This will adhere to metal,
as well as wood, and is used for the inside of camera, tubes, etc.

Sealing Wax for Bottles.--Melt together six parts rosin and one beeswax,
and add a small quantity of lampblack; or, if red is preferable,
add red lead. Common white wax is best, as most chemicals act
less upon it.