The Optical Magic Lantern Journal (February 1897)

32 The Optical Magic lantern Journal and Photographic Enlarger. by a battery of accumulators employed as a continuous indicator, was passed, during two hours, 1,300 cubic centimetres of gas collected and freed from carbonic acid, and in a baryta tube connected with the bulb there was only a scarcely perceptible ring of carbonate of baryta, indicating such a slight quantity of carbonic acid that analysis was impossible. From these experiments it was concluded that the products of combustion of a Manchester burner with acetylene do not contain the least trace of combustible gas containing carbon. JII. Incomupreres Comsustion or ACETYLENE AND PRODUCTION OF OXIDE OF CARBON. —Mr. Le Chatelier (Comptes Rendus, Dec. 30th, 1895), observed in the products of combustion of acetylene: carbonic acid, oxide of carbon, water steam, and hydrogen. Analysis of a dog's blood after the animal had inhaled the products of combustion mixed with air during 20 minutes ‘revealed the presence of 23.2 cubic centimetres | of oxide of carbon per 100 of blood. It is a considerable proportion, which explains the danger of death to the animal; therefore, when acetylene burns badly, it evolves a great deal of oxide of carbon. The same experiment was made with lighting gas; the dog died in a quarter of an hour, and the blood was almost completely oxycarbonated, containing 24 per cent. of oxide of carbon. Great care must be taken when employing acetylene or coal gas for heating to ascertain that the apparatus is not defective, as imperfect combustion of these gases would evolve a large and very dangerous amount of oxide of carbon. IV. Exptostve Mixtures or AIR AND ACETYLENE.—LExpPLosivE MIxTuRES oF AIR ‘AND Licutinc Gas.—From experiments made it results that mixtures of air and acetylene explode with much greater violence than air and lighting gas. Great care must be taken to prevent gas. We must contradict a certain writer who said “ Lighting gas becomes explosive when mixed with a small amount of air, whereas to make acetylene explosible the mixture is as considerable as it is impossible to realise.’’ One must guard against the explosive mixtures which acetylene gives with air ; that which gives ‘the most violent explosion is the mixture of 1 | escapes of acetylene | volume of acetylene and 9 of air.’’ (Comptes | _ cylinders or bags, and was totally unacquainted Rendus, April 13th, 1896.) V. Brivurancy oF THE ACETYLENE FLAME. HyaGirxneéE cr Sicur.—Mr. Viclle, Professor at the Conservatoire des Arts et Métiers, recently proposed employment of an acetylene burner as photometric standard. ‘*The gas compressed in a holder issues under a pressure of 30 centi: ; metres of water; it passes through a small conical opening conveying the air necessary for combustion, and burns in a burner of the Manchester type. The butterfly part of the flame, of uniform brilliancy, was determined by aid of the photometer and photography. The flame is surrounded with a double metal jacket which protects it against the surroundingair ; theactive part is limited by two diaphragms on either side, one, an iris-diaphragm, is worked by a graduated rod; the other may have openings of known diameter. Thus are obtained powers varying from 5 to 20 candle-power. The total flame represents 100 candles, and this power may be increased to 125 by extra pressure.” The brilliancy of the acetylene flame is such that if one gazes steadily for two minutes at the flame of a bat’s-wing burner and then shut the eyes, a persistent image of great brightness is perceived on the retina, the duration of which is really a cause of anxiety. It thus appears that acetylene is too dazzling for offices or rooms. Inventors should study the best means to abate this brilliancy, so as to prevent possible injury to the eyes. ap 1% *XC viv The Electric Light in the Optical Lantern.—No. 1V. By CECIL M. HEPWORTH. On eee electric are which gives us the Me 24 brightest source of artificial light ‘ A that we have applicable to the ‘es a) YESS: requirements of the optical lantern, ~~. is formed between two carbon points separated a small distance from one g} -” another, by the passage of electricity a across that gap. We have now in this series of articles studied this effect pretty thoroughly, but very little notice has yet been taken of the cause. It would not do for a lanternist to undertake to give an exhibition | with the limelight, no matter how perfect was his knowledge of the behaviour of oxygen and hydrogen in that connection, of jets and limes and all the other accessories of a limelight lantern if he knew nothing whatever of gas with the function of the regulator. And before an electric lanternist can hope to conduct a show with anything like credit to himself and his apparatus, or, indeed, without misbaps of @ More or less serious kind, he must know something of the nature, or at least of the