When the ozone is formed the phosphorus can be withdrawn, and the phosphorous-acid smoke washed out by shaking the bottle; it is distinguishable by its smell, and also by its action on test paper, prepared by painting with starch containing iodide of potassium on some Bath post paper; when this is placed in the bottle containing ozone, it changes the test blue, or rather a purplish blue. [Illustration: Fig. 105. V. A small voltaic battery standing on the stool with glass legs, S S, and capable of heating a thin length of platinum wire about two inches long, and bent to form a point between the conducting wires, W W.--N.B. The voltaic current can be cut off at pleasure, so as to cool the wire when necessary. A is the prime conductor of an ordinary cylinder electrical machine. B is the wire conveying the frictional electricity to the conducting wires of the voltaic battery, where the point P being the sharpest point in the arrangement, delivers the electrified and ozonized air.] Ozone is a most energetic body, and a powerful bleaching agent; if a point is attached to the prime conductor of an electrical machine, and the electrified air is received into a bottle, it will be found to smell, and has the power of bleaching a _very_ dilute solution of indigo. Ozone [Page 102] is not a mere creation of fancy, as it can not only be produced by certain methods, but may be destroyed by a red heat. If a point is prepared with a loop of platinum wire, and this latter, after being connected with a voltaic battery, made red hot, and the whole placed on an insulating stool, and connected with the prime conductor of an electrical machine, it is found that the electrified air no longer smells, the ozone is destroyed; on the other hand, if the voltaic battery is disconnected, and the electrified air again allowed to pass from the cold platinum wire, the smell is again apparent, the air will bleach, and if caused to impinge at once upon the iodide of starch test, changes it in the manner already described. (Fig. 105.) Ozone is insoluble in water, and oxidizes silver and lead leaf, finely powdered arsenic and antimony; it is a poison when inhaled in a concentrated state, whilst diluted, and generated by natural processes, it is a beneficent and beautiful provision against those numerous smells originating from the decay of animal and vegetable matter, which might produce disease or death: ozone is therefore a powerful disinfectant. The test for ozone is made by boiling together ten parts by weight of starch, one of iodide of potassium, and two hundred of water; it may either be painted on Bath post paper, and used at once, or blotting paper may be saturated with the test and dried, and when required for use it must be damped, either before or after testing for ozone, as it remains colourless when _dry_, but becomes blue after being moistened with water.