MAUNGATUA.

Otago Witness, Issue 1461, 15 November 1879, Page 11

MAUNGATUA.

(feom a correspondent.)

Mr W. H. Wicks delivered an illustrated leoture on chemistry in the schoolroom here, on Tuesday evening. There was a good attendance, and Mr Wicks was very successful in his experiments. The subject ohoseu was " water," aud was divided into eleven parts. At the conclusion of the lecture, Mr Halliwell, the local schoolmaster, proposed a vote of thanks to Mr Wicks, which was carried unanimously. The following is a resume of Mr Wicks' lectur.e :— Water is presented to our senses in three different states, viz., Bolid, liquid, and as a gas. It is composed of two gases, oxygen and hydrogen, united in the proportion of 81bs of oxygen to lib of hydrogen. Oxygen is an invisible oolourless gas, it has neither smell nor taste. It does not burn, but it is called a supporter of combustion. Combustion ia rapid burning. (Bxper., the burning of a splinter in oxy.) Some metals will burn in the air if they are first heated, while others require to be placed in pure oxygen. Air is oxygen very much diluted with another gas called nitrogen. Magnesium will bnrn^ in the air (exp. 2). This white powder is magnesia, a substance which you probably all know, as it is used as a medicine. It consists of this metal united with oxygen. Some metals like iron will not burn in the air, but will readily burn if heated and placed in oxygen. In this experiment it will be noticed that globule 3of melted iron fallto'the bottom of the vessel. It is not always necessary that the substance to be burned should be dry when exposed to the action of oxygen. A piece of phosphorus was then placed in a vessel of water and acid was poured on it, causing sparks of fire, the explanation being that the oxygen was given off (experiment 4). Phosphorus will not burn unless heated (experiment 5), but if divided into a very fine powder it will unite with the oxygen of the air without being heated (experiment 6). Hydrogen, the other gas found in water, is separated by decomposing the water by means of lime. * Hydrogen will not support combustion, like oxygen, but it will burn at the end of the tube (experiment 7). Hydrogen has neither smell, colour, nor taste, and is the lightest known substance ; it is on this account used for filling balloons. In filling a jar with it, it is necessary to pour the gas upwards, although this seems an anomaly. A. mixture of oxygen and hydgen if kept in the dark will not unite together, but if a light be applied they will explode with fearful violence.

The lecturer then shewed that some gases do not burn or support combustion, illustrating this by plunging a burning splinter and a lighted candle into carbonic acid, and thus extinguishing the lights. Carbonic acid (said the lecturer) exists in large quantities, and is the cause of death in many breweries, &o. The lecturer finished by reviewing the properties of oxygen, its necessity to enable life to exist in the world, for fires to born, &o.