Ultra-violet rays

OZONE A reactive form of oxygen the molecule of which contains 3 atoms of oxygen. In the ozone layer it protects the earth by filtering out ultra-violet rays. At ground level, as a constituent of photochemical smog, it is an imtant and can cause breathing difficulties. 

OZONE LAYER A thin layer of ozone that lies about 25 kilometres above the earth in the stratosphere. Forms a protective screen against harmful radiation by filtering out ultra-violet rays from the sun. 

Because of the potential hazard of release of unignited hydrocarbons at ground level, a flame scanner with alarm in the control house is included for each pilot. The flame scanner must be located so that interference of ultra violet rays from the main flame or other sources do not cause false readings. Ultraviolet detectors should be mounted such that they are looking straight down through the pilots toward the ground. The installation should also provide strainers in each gas or oil line to pilots. 

By applying ultra violet rays to the plate, light-hardening is promoted. When this process is completed the hardness should have been raised to 84-90 degrees of Shore D. (See Fig. 9). 

In the morphology of as-grown micro-diamond crystals, no essential difference was detected between T5tpe I and II crystals, which both take octahedral forms. This is clearly shown in Fig. 9.21 [21], in which the two t)tpes are compared by the transmittance of ultra-violet rays. There is no essential difference in morphology between Type II, which is transparent under the ultra-violet ray used, and Type I, which is opaque to the same wavelength. 

W7. Nernst has suggested that the hydrogen in lithium hydride plays the part of a halogen, and likens the reaction LiOH + H2=H20 +LiH with LiOH+HCl =H20+LiCl he shows similarities between lithium hydride and chloride in their crystalline form, at. vol., at. lit., heat of formation, coloration of ultra-violet rays, etc. The electrolysis of molten lithium hydride is also analogous with that of fused lithium chloride. Since lithium hydride is completely hydrolyzed in aq. soln., it is assumed that hydrogen acts as a very weak acid. 

Curve A represents the decomposition of mercury fulminate irradiated with ultra-violet rays, curve B the decomposition of ground mercury fulminate, and curve C the decomposition of ordinary (freshly-prepared) mercury fulminate. 

Carbon disulphide absorbs ultra-violet rays, a maximum absorption being reached when A is approximately 3250 A.3 The chemical constant is given by Nernst as 3-1. 

T. Urbanski, Malendowicz and Dybowicz [68] examined the behaviour of nitroglycerine (and of other nitric esters) exposed to ultra-violet rays and established that nitroglycerine irradiated once for a short period with a quartz lamp started to undergo slow decomposition which stopped only after an interval of 2-3 days. A sample of 3 g nitroglycerine was irradiated for 1 hr with rays from quartz lamp passing through a filter permeable to rays of 3200-4100 A whilst maintained at a temperature of 15°C. In order to test the decomposition of the specimen, from time to time 0.25-0.5 g sample of the substance were removed, shaken with water and the pH values determined. The following results have been obtained immediately after irradiation pH = 6.86 after 6, 24, 48 and 72 hr—6.12, 4.66,4.48 and 5.22 respectively. 

According to experiments by Deb [69] explosion of nitroglycerine can be provoked by intensive irradiation with ultra-violet rays (of 900 J strength), if the substance was previously heated to 100°C. 

The viscosity of nitrocellulose is also affected by prolonged exposure to sunshine primarily by ultra-violet rays. It is beyond question that these cause shortening of the molecular chain. (Donald [87], Fric [88], Breguet and Caille [89], Stark [78] and others). 

Direct sunlight or some other source of ultra-violet rays is essential for this preparation (p. 50). 

Ibid, Action of a-Rays of Polonium, X-rays onH Ultra-violet rays on Nitrogen Iodide and other Explosives , SocChimBullFr 53, 612—13 (1933) 12) W.E. Gamer C.H. Moon, The... 

Another method for measuring Volta potentials is to ionize the air between the plates, and adjust the potential applied to them until no current passes across the air gap. This method appears to have been used first by Righi2 (with ultra-violet rays as a source of ionization), later by Perrin and many later workers, using radium salts 8 Greinachcr,4 and Anderson and Morrison,6 pointed out that errors frequently arose if sources capable of ionizing the air in other parts of the apparatus than directly between the plates and it is well to use either a carefully shielded source of j3 or y rays or a radioactive source such as polonium, which gives off only a rays which have a range of a few centimetres only. This method is that used for the determination of the surface potentials of insoluble films as described in Chapter II. 

Sunlight can produce a slow but appreciable combination between the gases,1 the action being due to the ultra-violet rays. Ultra-violet radiation affects both detonating gas and water-vapour tending m each case to produce an equilibrium between the vapour and the constituent elements 2 with increase m intensity of the illumination the equilibrium shifts m favour of further dissociation, but the proportion of dissociated vapour at the position of equilibrium is very small. The process of combination probably proceeds by the stages 3... 

Synergistic effect of transparency to ultra violet rays and visible light rays, the strong Si-O-Si framework, and chemical resistance gives the HS-polymer excellent weatherability as one of the promising features. 

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