Photo-chemistry / by S.E. Sheppard.

  • Samuel Edward Sheppard
Date:
1914
Catalogue details

Licence: In copyright

Credit: Photo-chemistry / by S.E. Sheppard. Source: Wellcome Collection.

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    been used in one important photo-chemical inquiry.1 2 3 In general use at present are the Vernon Harcourt Pentane Lamp, and the smaller Simmance modification pf this. The former burns a mixture of gaseous pentane and air so as to give at ordinary barometric pressure a flame 2*5 cms. high. Its light is then equal to that of ten Parliamentary candles “ (see Fig. 3). The 10 c.p. Pentane-Harcourt lamp (Journ. of Gas Light- ing, p. 1252 (1898)) is used as standard in London. Pentane is obtained from American petroleum, B.P. about 40°, and S.G. between 0*6235 and 0*626. Air passes over liquid pentane, is saturated, and burns in a soapstone burner. The flame is restricted above by a chimney, and below there is a conical screen with an opening, through which the lower part of the flame radiates. The Hefner-Alteneck Amyl-acetate Lamp.—This burns pure amyl-acetate. The wick is circular, the wick-tube being a double cylinder of 8*3 mm. external and 8*o mm. internal diameter, 25 mm. in length; the whole of the interspace is filled by the lamp, which gives a flame 40 mm*, high from the edge of the tube some ten minutes after lighting. With all liquid-fed lamps the intensity rises on first lighting till a more or less constant maximum is reached. H. W. Vogel gives the following instructions for its use.:! The height of the flame is determined by the sight line over the two edges of the strip ab (see Fig. 4). To adjust, look through the point of the flame at the illuminated edge ab and regulate its height by screwing the disc at the side, so that the apex of the bright kernel of the flame just touches the under edge of ab. This point of the flame lies about half a millimetre below the furthest point of the external half-luminous mantle. 1 F. Hurter and V. C. Driffield, Photochemical Investigations, Jour, of Soc. Chern. Ind., 9, 455 (1890). 2 For completer details see F. Clowes, four, of Soc. Chem. Ind., 313 (1902) ; Dibdin, Jahrb. f. Client. Techtt., 26 (1888). 3 For complete description, method of use and determinations accord- ing to the Reichsanstalt at Charlottenburg, see Zeitschr. f. Instr.-Kunde, 13, 257 (1893).
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