Testing the hardness of metals

Testing the hardness of metals

CURRENT TOPICS. 407 Colloidal Barium Sulphate. Y. KATO. (Men*. Coll. Sci. and Eng., Kyoto, ii, I87.)--To a solution of barium acetate, prepared by d...

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CURRENT TOPICS.

407

Colloidal Barium Sulphate. Y. KATO. (Men*. Coll. Sci. and Eng., Kyoto, ii, I87.)--To a solution of barium acetate, prepared by diluting a gram-molecular aqueous solution with six times its volume of alcohol, was added an alcoholic solution of sulphuric acid, prepared by diluting a molecular aqueous solution with twice its volume of alcohol. The milky solution and jelly-like precipitate thus obtained were evaporated to dryness, under reduced pressure, at a temperature below 4o°C. Colloidal barium sulphate was thus obtained as a translucent, casein-like mass, readily soluble in water, the solution being fluorescent. The solution of the colloidal sulphate is, in general, coagulated by electrolytes, the coagulating power of different anions increases with their valency, according to Hardy's Law, and dissociating electrolytes have a higher coagulating power. Cations of high valency interfere with the coagulating action of anions. Testing the Hardness of Metals. A. F. SHORE. (Iron Age, lxxxvi, 9.)--This is a highly interesting and valuable paper for automobile engineers and those interested in the hardness of metals. It is pointed Out that there are many different kinds of hardness; viz., tensile hardness, cutting hardness, abrasive hardness, elastic hardness, static hardness, and shock hardness. According to Mr. Shore's view there is but one really important hardness, which may be defined as rigidity and resistance to penetration or deformation. Possibly this might be called tensile hardness. Measuring Aeroplane Altitudes. AUGUSTUS POST. (Amer. MaEch., xxxiii, 35.)--To accurately determine the altitude reached when W. R. Brookins broke the world's record for height with an aeroplane at Atlantic City, a base line 2 ~ miles long whs chosen. An engineer's transit was placed at each end of this base line with its telescope clamped in the vertical plane passing through the line, and by sighting upon the aeroplane as it passed above, the vertical angles at each end of this line were determined. Knowing the base and two angles of this triangle, the altitude was easily and accurately calculated. A recording barometer was used as a check. Full details are given in this interesting article. Also a description of a simple, but remarkably accurate method used b y the Wrights for ascertaining altitude. Such measurements will be of the utmost importance in finding the range of an aeroplane in war time. Scandium. SIR W. CROOKES. (Phil. Trans. Roy. Soc., A2o9, I5.)--Scandium has been found to the extent of more than I per cent. in the mineral Wiikite from Finland, and in small amounts in many other minerals. By a systematic series of fractionations it is possible to separate scandium from most associated elements; ytterbium is the most difficult to separate because its nitrate is decomposed almost as readily as scandium nitrate. In view of the VOL. CLXX, No. XoI9~3o