Science Siftings

New Zealand Tablet, 1 July 1915, Page 53

Science Siftings

By ‘Volt.’

Wood in Aeroplanes.

Many persons are wondering these days what material is being used in the construction of aeroplanes of the warring European nations. Constant flying/ service which continues day after day, has caused a belief that metal has supplanted wood to a considerable extent. As a matter of fact, the flying machines are made, with the exception of the engine and landing wheels, entirely of wood. The propellers of the aeroplane are, in most instances, made of numerous layers of. selected ash, which in addition to being strong and light, will not split under vibration or shock. Built-up layers of spruce, with mahogany centres, are also in use. . Spruce is used'in the construction of the frame, because of its markedly straight grain and freedom from hidden defects. - The Danger of Celluloid. It is well known that celluloid is highly inflammable and on various occasions has caused loss of life and property. The chemical process of its combustion has been studied by Doctor Panzer, of Vienna, and the results of his experiments show a way of dealing with a celluloid blaze. This substance does not ignite spontaneously ; but it was found that after extinguishing the flames of a piece of burning celluloid decomposition would still go on, and would continue even in a vessel filled with carbolic acid or steam. This shows that atmospheric oxygen is not necessary for decomposition; that a fire caused by celluloid can only with difficulty be put out with water, and that ordinary chemical fire extinguishers are useless. The flameless combustion starts at a temperature of but little over 212 degrees Fahrenheit, so that the decomposition may be started by a flame some distance away. The white vapors resulting from the combustion form an explosive mixture with air. To extinguish a celluloid blaze in a building is a most difficult task, if not impossible. Sources of Color’s. The ingenuity of the makers of pigments for the use of artists has been drawn upon so 3 heavily (says a writer in Harper ’.s Weekly) that the manufacturers have been obliged to employ for the purpose all manner of animal, vegetable, and mineral substances. Even the mummies of ancient Egypt have been utilised by the color makers. The corpse of the old Egyptian was preserved in the finest bitumen, and the remains thus treated in the centuries gone present on being unwrapped to-day an appearance quite like that of lightcolored leather. Now it has been found that when the bitumen and the leather-like remains are ground down by machinery there may be obtained therefrom a beautiful brown pigment especially prized by artists who paint portraits. This pigment is particularly effective in depicting certain shades of brown hair. Among the other colors obtained from strange sources may be mentioned Prussian blue. This is made by fusing the hoofs of horses with impure potassium carbonate. Sepia is the dark dluid discharged by the cuttlefish to render the water opaque for its own concealment when attacked by its enemies. The cochineal insect furnishes crimson and purple, lake and carmine, while ultram'arine blue is obtained from the precious metal known as lapis lazuli. Raw sienna is natural earth from Sienna, and when burned becomes burnt sienna. Gamboge is the yellow sap of a tree that grows in Siam.