Chemistry and Physics. 331 



SCIENTIFIC INTELLIGENCE. 



I. Chemistry and Physics. 



1. On the Existence of Suspended Matter in Flames. — It has 

 been observed by Stokes that when a beam of sunlight, con- 

 densed by a lens, is passed through a candle-flame, the area of 

 intersection of the double cone of light with the luminous envel- 

 ope is marked by two brighter patches of light of inappreciable 

 thickness which exhibit the polarization of light scattered by fine 

 particles — that is to say, when viewed in a direction perpendicular 

 to the incident light it is polarized in a plane passing through the 

 beam and the line of sight. These patches can be made more 

 conspicuous by viewing the whole through a cell containing cop- 

 per-ammonium sulphate solution, or through cobalt-glass. The 

 same phenomenon is shown by a luminous gas or ether flame but 

 not by the blue base of a candle flame or by a Bunsen flame, 

 even when rendered luminous with sodium chloride, or b}^ an 

 alcohol flame or by an ether flame just expiring for want of air. 

 The separation of carbon, or carbon associated with hydrogen, 

 thus rendered evident by its polarizing effect on light, is due to 

 the action on the volatile carbon compounds, in the absence of a 

 sufficient supply of oxygen to effect complete combustion, of the 

 heat evolved by the more complete combustion at the base of the 

 flame. In the case of the dying ether flame, the heat is probably 

 distributed over too large a mass of inert gases to effect the 

 decomposition. The thinness of the stratum of glowing carbon 

 is pi"obably due to the combined attack of oxygen on the outside 

 and carbon dioxide on the inside. — Chem. JVeios, Ixiv, 167; J. 

 Chem. Soc, Ixii, 111, February, 1892. G. f. b. 



2. On the use of Surface Tension in Analysis. — It is " well 

 known that any liquid may be made to roll upon itself in drops, 

 these drops being separated from the main body of the liquid by 

 a thin stratum of vapor. Gossart has applied this fact to the 

 detection and estimation of impurities in liquids, and finds it of 

 special value in the case of spirituous liquors. For this purpose 

 a drop is allowed to fall from the height of a millimeter upon the 

 concave meniscus at the edge of the vessel containing the liquid. 

 It is preferable to use a vessel having sloping sides so that the 

 meniscus has a hyperbolic section. By the addition of such sub- 

 stances > as citric acid or glycerin, the liquid is rendered viscous. 

 If two pure liquids be nsed, the sepai'ating film of vapor is imme- 

 diately absorbed and the drops of one liquid never roll upon the 

 other. If however the supporting liquid contains an impurity, 

 test drops of this same liquid will roll upon the supporting 

 liquid, provided either that the two liquids contain the same per- 

 centage of the same impurity, or that this percentage varies only 

 within fixed limits. With care these limits can be so far reduced 

 that it becomes possible to find the amount of impurity present 



Am. Jour. Sci— Third Series, Vol. XLIII, No. 256.— April, 1892. 

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