The Optical Magic Lantern Journal (February 1900)

The occasional heating and the possibility of a fire when the spent chloride is brought into contact with air and light in the operation of recharging the purifier, is an unpleasant phenomenon, but it is equally under complete control, if we may trust, as we entirely do, the latest information on the subject. Ahrens has found that chloride of lime when used alone does not exhibit this liability to become hot. It has been the custom with some firms to dilute the bleaching powder with sawdust, in order to render it more porous, and by increasing its surface make it a more energetic absorber of phosphoretted hydrogen. And it is precisely this mixture of chloride with sawdust which is principally liable to heat. Manifestly, there is no peculiar virtue in sawdust as a diluent; a host of other harmless indifferent substances are to be thought of on the spur of the moment. Inasmuch as sawdust has been shown to be harmful, some of these materials must be substituted. Ahrens and Benz both make suggestions; coarsely powdered brick, coke, slag, kieselguhr, etc., will serve. Ahrens also remarks that the chloride must be mixed either with very little water, or with avery large quantity of sawdust, to make it quite safe; but, we submit, the total avoidance of the organic matter of wood is distinctly more advantageous. Quite recently an accident occurred in a mill at Wiirtemberg, where chloride of lime mixed with keiselguhr was being used ; the water-seal of the purifier was blown out, the holder bell was lifted, the gas caught fire, and suffocated several workmen, who remained unconscious for several hours. purifying material was found to be pasty with water, although it had been introduced into the vessel inthe dry state. This catastrophe seems to have been due'to the gas passing directly from: the generator into the purifier very hot and loaded with moisture ; not improbably also the carbide was unusually bad, and the acetylene contained a notable proportion of ammonia. The trouble was aggravated by the employment of an abnormally large purifier ; for it is reported that some 90 times more chloride was present than was necessary to deal with the whole of the gas evolved by the generating apparatus. Thus we see that by keeping the original acetylene free from too much moisture, removing the ammonia, treating it with chloride of lime, diluted if necessary with some inert inorganic substance, and making it afterwards pass through a vessel of slaked lime, more of the impurities in the crude gas are extracted than | After the explosion the if the Frank or the Ullmann process be adopted. The operation is said to be simpler for a nonchemical attendant ; it is obviously far cheaper. The one disadvantage of the purified gas, its minute percentage of carbonic oxide, is far too trivial to be considered, and no fear need be felt that the half-spent material may become a source of anxiety by overheating, or the spent material a source of danger by actually catching fire. ws QOH oe se The Lantern and Kinetograph as aids to the Teaching of Languages. By WILHELM LEIFELD. WEA HE use which has been and is being V4 24 made of the lantern in schools and \ G ) colleges is well known. In techno (XSS! logical and scientific courses of i=“ instruction it is practically inve) dispensable. History and geography I” are also subjects in which lantern 2 illustration is of the greatest possible service, but up to the present the immense assistance which it is capable of rendering the teaching of foreign languages does not appear to have attracted the attention of teachers. When it does, there is no doubt that every class-room in every school must be provided with a lantern, or possibly with a kinetograph, which shall take tbe place of the grammar. How so? says the reader, who is wrestling to learn or to teach a foreign tongue. Well, wait a moment. You know that the usual methods of teaching a foreign language to a boy or girl at school are utterly wrong In principle. They are not Nature’s methods; they are not the methods by which everyone learns his own tongue without grammar and exercises. The really natural and scientific. method, . therefore, of learning a language is to imitate as far as may be the method by which one learnt one’s own. And how wasthat? Simply this: by the simple process of putting together at the same time into the mind two things :—(1) the idea or mental picture of a thing, and (2) its name or title. Thus we were shown a cow, told that it was a ‘‘cow,”’ and straightway a big black, white, or piebald beast, with horns, was for ever associated in our minds with the name “cow.” We learnt it easily, and yet unlike most things learnt easily, we never forgot it. The same thing applied to verbs. We saw a man running, and we were told that to.do so was “ torun”; and the two things—the act and oa as