Description
This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1922 Excerpt: …from the above standard atmospheric conditions may be corrected by the equation: I = In 1-0.00567 (-8) + 0.0008 (6-760), where / is the actual intensity, In the standard intensity, e the liters of water vapor per cubic meter of air and b the barometric height. The color and intensity of the flame are convenient for practical purposes, especially for the measurement of the illuminating power of gas. An added advantage in the testing of luminous flames of all sorts resides in the fact that their intensities are affected by atmospheric variations in a manner corresponding quite closely to the changes in the pentane lamp, whereby somewhat troublesome corrections are avoided. Carcel Lamp.–The Carcel lamp is the recognized standard of luminous intensity in France. It has a central-draft ring burner fitted with a wick of the light-house type burning colza oil. Its standard intensity is 9.61 international candles. Standard candles are now discredited for all accurate work, though still used extensively in the routine testing of gas. Incandescent Electric-lamp Standard.–The incandescent electric lamp a superior to all other working standards where corrections for flame luminosity due to atmospheric variations are not required. Carefully selected carbon-filament lamps aged by burning until the hot resistance is constant maintain their candle-power sensibly unchanged for a period of 10 hours or more. With the most precise photometric apparatus such lamps may be standardized with the mean error of any single determination not exceeding say from 0.5 to 1.0 per cent. Lamps are standardized for use in a fixed position or in rotation about the principal axis. No difference exists between the precision of the two metru-ds. Lamps are standardized in terms of a defini…
