MINUM ELECTRODES.--When this material is used as the electrodes in
water, hydrate of aluminum is formed, or a compound of hydrogen and
oxygen with aluminum. The product of decomposition is a flocculent
matter which moves upwardly through the water, giving it a milky
appearance. This substance is like gelatine, so that it entangles or
enmeshes the germ life and prevents it from passing through a filter.

If no filter is used, this flocculent matter, as soon as it has given
off the gases, will settle to the bottom and carry with it all
decomposed matter, such as germs and other organic matter attacked by
the oxygen, which has become entangled in the aluminum hydrate.

ELECTRIC HAND PURIFIER.--An interesting and serviceable little purifier
may be made by any boy with the simplest tools, by cutting out three
pieces of sheet aluminum. Hard rolled is best for the purpose. It is
better to have one of the sheets (A), the middle one, thicker than the
two outer plates (B).

[Illustration: _Fig. 91._ PORTABLE ELECTRIC PURIFIER]

Let each sheet be 1-1/2 inches wide and 5-1/2 inches thick. One-half
inch from the upper ends of the two outside plates (B, B) bore bolt
holes (C), each of these holes being a quarter of an inch from the edge
of the plate. The inside plate (A) has two large holes (D) corresponding
with the small holes (C) in the outside plates. At the upper end of this
plate form a wing (E), 1/2 inch wide and 1/2 inch long, provided with a
small hole for a bolt. Next cut out two hard-rubber blocks (F), each
1-1/2 inches long, 1 inch wide and 3/8 inch thick, and then bore a hole
(G) through each, corresponding with the small holes (C) in the plates
(B). The machine is now ready to be assembled. If the inner plate is 1/8
inch thick and the outer plates each 1/16 inch thick, use two small
eighth-inch bolts 1-1/4 inches long, and clamp together the three
plates with these bolts. One of the bolts may be used to attach thereto
one of the electric wires (H), and the other wire (I) is attached by a
bolt to the wing (E).

[Illustration: _Figs. 92-95._ DETAILS OF PORTABLE PURIFIER]

Such a device will answer for a 110-volt circuit, in ordinary water. Now
fill a glass nearly full of water, and stand the purifier in the glass.
Within a few minutes the action of electrolysis will be apparent by the
formation of numerous bubbles on the plates, followed by the
decomposition of the organic matter in the water. At first the
flocculen