SCIENCE SIFTINGS

Wanganui Chronicle, Volume LXXXI, Issue 18957, 7 March 1924, Page 7

SCIENCE SIFTINGS

CORROSION IN METALS. Detailed study has brought out for the first time the market difference in the mechanism of corrosion with different metals. This discovery promises to prove of the greatest importance from a practical point of view as well as in leading to a further elucidation of the whole question of corrosion, says a report by Mr W. H. J. Vernon, and issued by the British Non-ferrous Metals Association. Three different types of tarnishing have been distinguished in the first type, represented by copper. The tarnish film actually protects the metal from further attack, the progress of tarnishing becoming slower and slower as exposure proceeds. This is accounted for by the supposed continuous layer which the tarnish film forms, and the consequent difficulty the corroding constituents of the air find in reaching the underlying metal. In the secohd type the tarnish is neutral, and the attack proceeds steadily—for instance, zinc in a dry atmosphere. In this case, says the Birmingham Post, quoting the above report, it is probable that the film is pervious to the air. Finally, the corrosion whilst starting off fairly slowly may become accelerated, and this forms the third type exemplified by iron. It is suggested that hero the corrosion product—rust—assists in the attack. “Some metals, such as zinc, brass, etc., may follow more than one type of progress according to the atmospheric conditions, or even to the thickness of the famish film. For instance, with brass the attack first proceeds uniformly, but later the film exhibits a protective influence, and the attack slows off.” THE MIRACLE OF MOUTH WATERING. When you hop out of bed in the morning and arc speeded in your dressing process by the smell of bacon and eggs frying in the kitchen, if you take the time you will observe that your mouth is watering. Pavlov, the great Russian physiologist, found a dog was shown his familiar feeding dish, even if it were empty, certain glands iu his mouth immediately got into action and liberated a 3 having the same chemical composition as that produced by snuffing food. Many of us have had this involuntary mouth-watering experience. “Psychic reflex” is the polite physiologist ’s name for such excitations. Th«n after the food has started on its downward journey there arc millions of other minute cells pouring out chemical substances to aid in the digestive process. The chemist (says the Country Gentleman), cannot yet rival the laboratory of the living organism where the starch of our bread, the fat of our butter, the proteins of our meat, all insol- | üble in water, are wonderfully transformed into substances that are smoothly and rapidly taken into the blood.

The enzymes produced in living cells that effect these transformations have not even been isolated by the chemist. They aid in producing carbo-hydrates, alkaloids, glucosides and other complex substances. The biologist and chemist would be thankful if he could only learn a little more about the chemicals of the body. Making them is the distant and only dreamed-of goal. If mouth watering was not such a common thing, h.ow startling would be the news of its discovery. We ate just a bunch of living everyday miracles. NATURE’S TEMPERATURE CONTROL. You put water into the radiator of your automobile or tractor to keep the motor from overheating and you put a bucket or two of water into your cellar to keep the potatoes from freezing. Aside from the facts that water is made from two gases, hydrogen and oxygen, and that it is used to put out [fire even though it is composed of one [very inflammable gas and anothej that [permits the fire to burn, water has some remarkable properties. In the first place, it takes more heat to raise a given quantity of water one degree in temperature than it does any other substance. If the blacksmith should drop one pound of iron at a temperature of 212 degrees Fahrenheit into one pound of water 32 degrees Fahrenheit, the temperature of the water would be raised but 18 degrees, while the temperature of the iron was lowered 162 degrees!

It takes about five and a third times as much heat to convert a given quantity of water already at the boiling point into steam as it does to heat the water all the way from the freezing point to the boiling point—that is, if we had one pail of water already at the boiling point, 212 degrees Fahrenheit, it would take as much heat to convert it into steam, as, it would to heat five and a third buckets of water all the way from the freezing, 32 degrees Fahrenheit, to the boiling point! Thus the instructions for small cars say not to worry if the water in the radiator boils a bit.

The temperature of ice is normally 32 degrees Fahrenheit, and the temperature of water just before it begins to form into ice is the same. But it takes as much negative heat to freeze a bucket of water as it does to bring that bucket of water from 176 degrees Fahrenheit all the way down to the freezing point. No wonder wo put a tub of water into the cellar along with the potatoes. Just think for a moment, now, that three-quarters of the earth’s surface is covered with water, and that plants and animals are composed largely of water. Surely nature has made good use . of a marvellous temperature control.— Weekly Telegraph. BUILDINS THAT WILL SWING. ’ In the case of steel-framed buildings an attempt has been made by force majeure to limit the destructive effects of earthquakes by proportioning the steel framing with large reserves of strength, particularly in the matter of what would commonly be called wind brac-i ing, this being made to resist the forces many times greater than that of the wind proper, and care being taken to ensure' a true continuity in the makeup of the stanchions—even so, it was not expected that screen walls or partitions would be immune from damage. Notwithstanding the more or less favourable accounts given with respect to the behavious of some of the more recent structures in steel, or in reinforced concrete, it is clear from the.statements of unbiassed eye-witnesses that not one of these escaped damages —generally serious, or complete collapse. An entirely new treatment of the problem would seem to be necessary. This may be found in the fundamental principle that -the building should be so supported as to be unaffected by horizontal earth movements, which may be secured by so supporting the structure that it docs not of neces- 1 sity move as the earth moves, to be achieved by suspending the building by tension rods from stable steel frames by suspension—in the case of light structures—from flexible steel uprights, or by support from balls of cast iron, steel, or granite.

The last-named method, though not new to the writer, has recently been proposed by Professor Bailey Willis, of Stanford University (U.S.A.) Horizontal movement of the earth’s surface would not then disturb the building which, by virtue of its mass, would remain still. The measurement of earth tremors is 'now, by some instruments, effected by application of the same law of inertia. A sound principle in structural design is that sudden displacements, involving the development of force, should either be adequately met by strength provided, or accepted by yielding that is harmless. The arrange-, ment proposed would seem to meet the last-named condition in great measure, but the writer does not yet see any practicable method of dealing with the greatly less destructive vertical movements. In the Nino-Pwari earthquake of 1891 a 9in horizontal range was observed, while at Tokio in 1894, though the range was but 3in, the rate of acceleration was 3ft. per sec. per sec. Generally the range is quite small, and acceleration seldom greater than 2in. per sec. per see.—Engineering.