Part 2 (1/2)

27 Always take the zinc fro, or even if you have no use for the cell for a few minutes The zinc and fluid are rapidly destroyed in bi+chromate cells even when the circuit is open Alash the carbon and zinc as soon as you take them from the fluid

APPARATUS 16

_28 Battery Fluid_ For 2-fluid cells (App 7), a saturated solution of copper sulphate (blue vitriol) is needed Place solass jar, ater, stir the as it is dissolved A few extra crystals should be left in the stock bottle so that the solution will always be saturated

APPARATUS 17

_29 Vinegar Battery Fluid_ For a few of the experiar does well as the exciting fluid

This may be used with the copper and zinc or carbon and zinc elear and App 4 or 5 is sufficient to show many of the simpler experi brine,ordinary salt in water, will produce quite a little current with App 4 or 5 The presence of the current is easily shoith the astatic detectors

APPARATUS 19

_31 Measures for Water, Acids, etc_ If you do not own a graduated glass, such as druggists use forplan will be found useful In theof battery fluids, etc, while it is not necessary to be absolutely exact, it is necessary to know approxilass pint fruit jar may be taken as the standard This holds 16 fluid ounces, or 2 ordinary teacupfuls A teacupful may then be taken as 1/2 pint, or 8 fluid ounces You can probably find a small bottle that will hold 1 or 2 oz, and you can easily tell howthe number of times it is contained in the pint can

A sli 1/2 pint can belines on it with the sharp edge of a hard file The lines should be placed, of course, so that they will sho much liquid you must put into it to make 1 oz, 2 oz, etc Instead of the file marks, a narrow strip of paper may be pasted upon the bottle, and the divisions shown by lines drawn upon the paper

APPARATUS 20

_32 To Aamate Battery Plates_ To keep the zinc plates or rods in cells fro eaten or dissolved when the circuit is opened, they should be a of mercury

The local currents (see text-book) aid in rapidly destroying the zinc, unless it is aamate copper plates--merely the zinc ones

33 Place a few drops of mercury in a butter dish Dip the zinc into the solution of App 14, then lay it upon a flat board This is necessary with thin sheet-zinc, as it becomes very brittle when coated withIf you also dip a very narrow piece of tin into the dilute sulphuric acid, you can use this as a spoon and lift one drop of mercury at a ti the tin upon the zinc, the mercury will leave the tin Put the mercury only where the zinc will be under the solutions in the cell, then rub the drops around with a small cloth that has been dipped in the acid The zinc will becoet too ive it a thin coat, as it will make the thin zinc so brittle that it will very easily break

Aamate both sides of the zinc

CHAPTER III

MISCELLANEOUS APPARATUS AND METHODS OF CONSTRUCTION

APPARATUS 21

_34 For Annealing and Hardening Steel_ (See text-book for reasons why some parts of electrical apparatus should be made of hard steel, while other parts should besteel so that you can bend it without breaking it, heat it in a candle, gas, or alcohol flame until it is red-hot; allow the steel to cool in the air slowly

36 To harden steel, heat as before, then suddenly plunge the red-hot piece into cold water This will make the steel very hard and brittle

S them between two pieces of wood