The Art of projection and complete magic lantern ... - Yesterday Image

—i63It is advisable to fill the trough with water, by this means the shadowson the tubes are avoided.UDecomposition of a Salt. With tank prepared as above theshaped tube is filled with a solution of iodide of starch, containing asmall quantity of bromine, this solution is colourless, when the current ispassed the positive branch assumes an orange colour, whilst the negativeis blue.These are a few of the many changes that may be brought about byelectrolysis.I.—CHEMICAL RE-ACTIONS.The greater number of the usual chemical re-actions can be effectedin the trough. If the coloured solutions are too dark, they should bediluted. The small glass funnel or pipette will serve for introducing there agents, but its end must not be plunged into the salt contained in thetrough, so as to stop up the capillary tube by what is precipitated ;there agents must be put in drop by drop, or in a minute stream, then theeffect is more striking. The re-agent may also be introduced by meansof the spoon, which must be gently shaken in order to mix the liquidsby degrees. Here are some of these re -actions as examples:I St. Put into the trough a solution of sulphate of peroxide of iron,add, drop by drop, a solution of ferro cyanide of potash, the result willbe Prussian blue.2nd. Fill the trough with a solution of sulphate of copper— liquidblue—add a little ferro-cyanide, the colour resulting will be reddishbrown.3rd.Fill the trough with the same solution of sulphate of copper, addsome ammonia, changing to a green tint, precipitating a cloudy grey,add some more ammonia when the precipitate will dissolve and thewater will assume a magnificent blue colour—sky blue.4th. Fill the trough with sulphate of zinc, add ammonia, drop bydrop, there will be a coagulated precipitate of a steel grey colour ofquite a peculiar shape.5th. Fill the trough with a very diluted solution of nitrate of silver,add a solution of sea-salt or chloride of sodium,be chloride of silver, not unlike snow in appearance.and the precipitate will6. Fill the trough with a solution of chlorate of barium, add, littleby little, diluted sulphuric acid, the precipitate will be in the form of finegranules of sulphate of baryta.L2