Obscuring power of white smokes

Obscuring Power of White Smokes. The total obscuring power, TOP, of a white smoke agent used for screening purposes, is obtained by multiplying the product of volume, in cubic ft or smoke produced per lb of material, and the reciprocal of the smoke layer, in ft, necessary to obscure the filament of a 40-watt Mazda lamp. The TOP for some white smoke agents, at low altitudes where atm constituents are plentiful, is given in Table 1... 

Properties Pale-yellowish, translucent, crystallizable solid of waxy consistency. Sp, gr, 1.82 at 20°. M. P. 44.1°. B. P. 280°. Spontaneously inflammable in air at normal temperature gives off dense white smoke, consisting of phosphorus pentoxide and phosphoric acid. The former has a very high obscuring power. White phosphorus has the greatest total obscuring power (T. 0, P.) of all smoke agents. 

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