Lecture on Water.

Wairarapa Standard, Volume XVIII, Issue 1764, 27 November 1885, Page 3

Lecture on Water.

(Continued.; There is however a very safe way of petting ij "drogen gas by the use of toJium mixed with mercury forming what is called an amalgam. To make the sodium amalgam put a little mercury into a mortar and press into it with the pestle a small piece of souiunt. The tvo metal i combine with a slight explosion. The amalgam is very different from its cinstitnects for i' is solid and bard. (Exp o) I’Uee a piece of this amalgam under water in a glass jar and cover it with a funnel. Bubbles of gas vi-:e from all parts of the amalgam and pass up the funnel. Ey inverting over the funnel a tube filled with water, ‘he gas may le collected and tested. On testing a tnbeful of the pas at a flame as Lefore the slight explosion and burning of the ga, with a pale bine flame denotes hydrogen. tiedium au J patassium unaided can decompose water, tut the metal zinc requires the presence of seine acid to effect this. The acid serves to keep the surface cd the metal always c.ear, otherwise the outer part of the zinc weak! combine with the oxygen forming a coating over the zinc and this coating or rust v.\,n!a prevent further decomposition of the water. The apparatus often used fur this experiment is a two-necked bottle specially made for the purpose, bat au ordinary pickle bottle will servo equally well. The bottle must 1o- tightly fitted with a bung or cork through wusen two tubes are passed. One tale reaches to the bottom of the bottle and is a safety tube to allow escape ol the liquid and gas in event of too hurried production ct hydrogen. The other tube dots not reach below the cork and serves as a delivery tube. Piace a tablespooufal or two of granulated zinc in the hydrogen bottle and cover the zinc with water. Then replace the cork with the tabes. Ivo action has as yet taken piace, but (Exp 4) on pouring in a little hydrochloric acid a mo.-i energetic chemical action is set up. Tue acid clears the surface of the zinc, which at once attacks the water and breaks it up. The hydrogen gas is set free and escapes by the delivery tube. The end of the delivery tube is under an iuveited bottle full of water and standing in a trougli of water. The light gas rises inside the bottle driving down the water, and very soon the bottle is filled. In performing this experiment one caution is necessary, since a mixture of hydrogen with the oxygen of the air is explosive ; always allow the gas time enough to drive the air out of the generating bottle before placing the end of the delivery tube under the collecting bottle.

Iron filings or lun.L.gs may be used in the place of zinc, but the gas produced will be very impure. There is another way of using iron to decompose water but the experiment requires a little trouble in putting the apparatus together. (Exp o.J A short length of iron pipe is passed through a furnace, by which it can be made red hot. This tube is filled with iron tilings and turnings. One end of the iron tube is connected with a flask containing water, the other end is fitted wdb a delivery tube. Heat the pipe and filings red hot, and then boil the water in the flask so that a current of steam may pass through the iron pipe among the filings. The iron breaks up the steam, combines with the oxygen forming iron rust, and allows the hydrogen to pass on to the delivery tube where it may easily be collected.

The process shewn in Exp. 4 is however the readiest wav of petting hydrogen gas in quantity and we shall use it to get sevcial jars fall of hydrogen. Having filled oar \as we may experiment with the gas to ascertain the properties of hydrogen.

(Exp 6.) Hydrogen is the lighest suband its lightness may be shewn two ways. Firstly you notice that containing it have to be kept mouth downwards to retain the hydrogen. It is possible to pour hydrogen gas up through the air from one bottle to another. We are accustomed to pour substances downward from one vessel to another, nut that is because most common substances are heavier than air. This bottle at present contains no hydrogen ; invert it and place one of the hydrogen jars mouth upwards under it. Test the Lottie now with a lighted splint Or taper and the hydrogen gas is f.iund to Lave poured upwards and paitly tilled the bottle. A light toy balloon filled with hydrogen gas readily ascends, as hydrogen gas is so much lighter than air, and in fact hydrogen was at fiist used to fill ordinary balloons.

Hydrogen £*- is combustible. (E-*p 7.) Hold a lighted splint to month of a jar fall of hydrogen and the gas takes fire, burning with tire usual pale blue, almost invi-ible flame of hydrogen. If the lighted splint he pushed np into the hydrogen gas. the flame is at once put out, shewing that although hydrogen gas is combustible it does not support combustion. Another way of shewing the combustion of hydrogen is to substitute a glass tube for the ordinary delivery tube of a hydrogen bottle, a tnbe drawn oat to form a very fine nozzle. As soon as all the air is driven out of the bottle the hydrogen gas may safely be lighted at the nozzle. Applying the light before the air is driven cut would cause a serious explosion. To ensure safety collect a little of the gag from the jet in a test tube and test the gas r.t a flame. When the gas in the tube taks s lire and burns (juietly then the gas at the jet may safely be lighted. If a cool glass jar be held over the hydrogen flame a mist soon forms inside the jar, and this increases until at last drops or beads of water ran down inside the jar, for the burning or combustion of hydrogen is simplv its combination with the oxygen of the air to form water.