Ultra-violet lamp

Purification of anthracene. Dissolve 0-3 g. of crude anthracene (usually yellowish in colour) in 160-200 ml. of hexane, and pass the solution through a column of activated alumina (1 5-2 X 8-10 cm.). Develop the chromatogram with 100 ml. of hexane. Examine the column in the hght of an ultra-violet lamp. A narrow, deep blue fluorescent zone (due to carbazole, m.p. 238°) will be seen near the top of the column. Immediately below this there is a yellow, non-fluorescent zone, due to naphthacene (m.p. 337°). The anthracene forms a broad, blue-violet fluorescent zone in the lower part of the column. Continue the development with hexane until fluorescent material commences to pass into the filtrate. Reject the first runnings which contain soluble impurities and yield a paraffin-hke substance upon evaporation. Now elute the column with hexane-benzene (1 1) until the yellow zone reaches the bottom region of the column. Upon concentration of the filtrate, pure anthracene, m.p. 215-216°, which is fluorescent in dayhght, is obtained. The experiment may be repeated several times in order to obtain a moderate quantity of material. 

In the case of colourless materials, the separated substances may sometimes be rendered visible on the column by fluorescence, excited by an ultra-violet lamp. However, with colourless materials it is usually best to continue passing solvent down the column till all the sample has been washed through die column by the mobile phase. The mobile phase which leaves the column and now contains the solute molecules is called the effluent or eluate and it is collected as a number of fractions or cuts at different times. The collection of liquid fractions (especially if the number of fractions is large) is both tedious and time-consuming so that, in practice, some form of mechanical device is employed. An automatic fraction... 

Visual measurement of the thiochrome fluorescence is possible using narrow non-fluorescent tubes, the contents of which are matched in a dark room with an ultra-violet lamp. The test solution and a strong aneurine standard are oxidised and extracted under exactly similar conditions together with a blank from which the ferricyanide has been omitted a measured volume of the test solution is matched against addition of the standard to the blank. The tubes are inclined at an angle of 60°, but they must not be exposed longer than necessary, since the fluorescence is unstable in ultra-violet light. The final comparison is made when the volumes have been equalised. 

If further information is required about the constitution of the water-soluble alkaloids the ergometrine and ergometrinine may be separated by paper chromatography and a rough estimation of the respective alkaloid contents made by comparison of the intensity of fluorescence under an ultra-violet lamp of sample spots with standard spots. 

Removal of spots from chromatograms Remove the papers from the frame, if one is used. Use either of two methods for spot location and removal for analysis. Method (i) is much to be preferred, but method (ii) can be used when no ultra-violet lamp is available. Even when method (i) is used, it is still desirable to spray one of the papers as in the first part of method (ii) in order to confirm the position of reducing spots. 

An ultra-violet lamp suitable for use while titrating has been introduced by Messrs. Baird and Tatlock (London) Ltd., and it and the appropriate fluorescent indicators can be obtained from Messrs. Hopkin and Williams Ltd., of 16 St. Cross Street, London. 

High voltage hydrogen discharge lamps which give continuous radiation in the ultra-violet can be constructed quite simply and elaborate designs are unnecessary for many purposes. A very simple... 

Light source. The most suitable light system examined was a Chromato-Vue Model C-3 from Ultra Violet Products, Inc., San Gabriel, CA. The light source was a GE G15T8, 15-W, Germicidal, 2537 bulb. The mercury lamp emitted radiation maxima at 254, 265, 280, 302, 313, 365, 405, and 436 nm. Radiation from this source passed... 

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. 

The E.B.B. Atmospheric Burner (Kelvin, Bot-tomley and Baird).—This lamp (Fig. 46) is a very convenient source of ultra-violet and monochromatic illumination. The quartz tube, which is not evacuated, is incompletely filled with air-free mercury. The current passes from the + electrode A to the — electrode B through the mercury,... 

Ultra-violet light, such as that emitted by a mercury-vapour lamp, exerts a powerful germicidal action on water and ice. In a series of experiments earned out at Marseilles it was observed that a lamp working with 3 amperes at 220 volts destroyed pathogenic organisms in water within a radius of 2 inches in two seconds.2 In order to ensure complete sterilisation m a stream of water, the latter is made to flow, by... 

By exposure to the light from a mercury vapour lamp in presence of oxygen and chlorine, decomposition takes place, and as an intermediate product, a compound of the formula COCl is formed. By exposure to ultra-violet light chlorine and carbon monoxide are formed. ... 

Samples oi me mixture were anaiysea m me molecular-u.v. aetecuon moae. For chromatogram A in Figure 15 the arsenic lamp (193.7 nm) without beckground correction was used as an ultra-violet source to detect volatile molecular species. Two peaks are observed for this mixture with retention time 95 + 4 s and 110 + 4 s. It was established independently that under these GC conditions (i.e. column 42 + 2 °C, isothermal) the retention times for the components of the mixture are ( 113)3 As, 93 +3 s ( 113)2 Se, 92 + 2s ( H3) Sn, 109 +2 s. 

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