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Heat treatment of steel
96
CURRENT TOVXCS.
phide is, at the most, about 2. 5 per cent., and material containing only monosulphide is considerably improved by the addition of calcram oxide. Starch, up to 4 per cent., increases phosphorescence, but a larger proportion diminishes phosphorescence. The period of photo-chemical induction requisite for exciting maximum phosphorescence is shorter for stones of comparatively simple composition and high metal content than for those of more complex composition and low metal content, and the rate of decay is correspondingly less in the latter. Confinement in various gases--e.g., chlorine, ammonia, and hydrogen sulphide--and mixing with organic dyestuffs or other so-called optical sensitizers, does not increase the phophorescence. Pressure is distinctly unfavorable; grinding causes a change of color and reduces phosphorescence. Exposure to light also changes the color to an extent dependent on the composition of the stone; but there is no apparent connection between the phosphorescent power and the readiness with which the color changes. Colloidal Sulphur. M. RAFFO and J. MANCINI. (Z. Chem. Ind. Kolloide, ix, 58.)--The stability of the colloidal sulphur solution prepared by one of the authors was due to the presence of sulphurie acid and sodium sulphate. Further experiments have now shown that the greatest stability is reached when the solution contains definite proportions of these substances, viz., 6.4 to 7.0 per cent. of sulphuric acid and 3.76 to 3.93 per cent. of sodium sulphate; the solutions contained 2.6 to 2.8 per cent. of sulphur. Coagulation experiments with salts of potassium, sodium, magnesium, zinc, aluminum, and chromium showed that potassium salts coagulate the colloidal sulphur much more readily than salts of other metals, and the iodides are the most effective of the alkali salts. 4N solutions of sodium salts precipitated approximately twice as much sulphur as 2N solutions did. Heat Treatment of Steel. H. HANEMAN. (Stahl und Eisen, xxxi, 1365.)--Pieces of steel wire, o.5 cm. in diameter and 20 cm. long, containing from o.99 to 1.56 per cent. of carbon, were heated to temperatures varying from 75°o C. to II5 o° C. and quenched, either in water or in a lead-tin bath, at 3oo ° C. Quenching at the higher temperature gave the highest tenacity. The tabulated results of the mechanical tests of hardened steels, after tempering in rape oil at temperatures from Ioo ° C. to 65°o C., show that it is not possible to obtain the same results by direct quenching in oil or in a lead-tin bath as by quenching in water and subsequently tempering. To determine the influence of time on tempering---~.e., whether heating at 5oo ° C. for a few seconds would produce the same structure as heating at Ioo ° C. for many hours---~pieces of steel containing o.87 per cent. of carbon were heated to varying temperatures for different periods of time, and then examined for
CURRENT ToPIcs.
97
scratch hardness, loss of weight in a I per cent. acid solution, the amount of carbide, and microscopically. It is concluded that hardened steel always tends to change into a-iron and free cementite. Although this change proceeds imperceptibly at ordinary temperatures, it takes only a few seconds at 65 °0 C. and some hours at IOO° C.
Silver, Tin, Lead: the Ternary System.
N. PARRAVANO.
(Ga~. Chim. Ital., xli, 813.)--This paper is a thermal and microscopic study of ternary alloys of silver, tin, and lead. All the ternary alloys are composed of the four solid phases, mixed crystals of silver and tin, mixed crystals of lead and tin, the compound Ag3Sn, and crystals of tin. The system contains two non-variant points, one of which, at about 3oo ° C., is a transformation point, while the other, at about 175 ° C., is an eutectic point. The ternary eutectic contains 63.4 per cent. of tin, 35.6 per cent. of lead, and I per cent. of silver. The transformation point is very near the binary lead-silver eutectic point, and the ternary eutectie point is very near the binary tin-lead eutectie point. This paper has 23 microphotographs.
Paper Pulp from Eucalyptus. ANon. (Paper Making, xxx, 376.)mSamples of pulp of excellent quality have been prepared from the eucalyptus (blue gum) which has been planted over large areas in Southern California. The pulp is strong, clean, and slightly reddish, owing to the action of the alkali. Experiments with this wood as a raw material for paper pulp have been carried out at Washington and leave no doubt that it is suitable for the purpose. A sufficient growth of blue gum may be obtained in four to six years; three years after cutting the stump yields a further good growth. Preservative Treatment of Poles. W . H . KEMPFER. (Forest Service Bull., 84, I 9 I I . ) - - A s the pressure method of treatmenl~ with creosote is comparatively costly, investigations were directed to simpler and cheaper methods, which could be employed locally. Special attention was given to the seasoning of the timber, and investigations were conducted with the object of ( I ) testing the efficiency of various wood preservatives and of the application of varying amounts; (2) developing a method for impregnating the butt, as the portion of the pole most subject to decay; (3) designing inexpensive apparatus for local use in application. The timbers used were chestnut, three kinds of cedar, and three kinds of pine; and six different commercial preservatives were tried. The conclusions reached were: The reduction in the weight of poles by seasoning is generally from 16 to 3° per cent., and thorough seasoning is an essential preliminary to preservative treatment. Poles cut during autumn and winter lose weight less rapidly but more
CURRENT TOVXCS.
phide is, at the most, about 2. 5 per cent., and material containing only monosulphide is considerably improved by the addition of calcram oxide. Starch, up to 4 per cent., increases phosphorescence, but a larger proportion diminishes phosphorescence. The period of photo-chemical induction requisite for exciting maximum phosphorescence is shorter for stones of comparatively simple composition and high metal content than for those of more complex composition and low metal content, and the rate of decay is correspondingly less in the latter. Confinement in various gases--e.g., chlorine, ammonia, and hydrogen sulphide--and mixing with organic dyestuffs or other so-called optical sensitizers, does not increase the phophorescence. Pressure is distinctly unfavorable; grinding causes a change of color and reduces phosphorescence. Exposure to light also changes the color to an extent dependent on the composition of the stone; but there is no apparent connection between the phosphorescent power and the readiness with which the color changes. Colloidal Sulphur. M. RAFFO and J. MANCINI. (Z. Chem. Ind. Kolloide, ix, 58.)--The stability of the colloidal sulphur solution prepared by one of the authors was due to the presence of sulphurie acid and sodium sulphate. Further experiments have now shown that the greatest stability is reached when the solution contains definite proportions of these substances, viz., 6.4 to 7.0 per cent. of sulphuric acid and 3.76 to 3.93 per cent. of sodium sulphate; the solutions contained 2.6 to 2.8 per cent. of sulphur. Coagulation experiments with salts of potassium, sodium, magnesium, zinc, aluminum, and chromium showed that potassium salts coagulate the colloidal sulphur much more readily than salts of other metals, and the iodides are the most effective of the alkali salts. 4N solutions of sodium salts precipitated approximately twice as much sulphur as 2N solutions did. Heat Treatment of Steel. H. HANEMAN. (Stahl und Eisen, xxxi, 1365.)--Pieces of steel wire, o.5 cm. in diameter and 20 cm. long, containing from o.99 to 1.56 per cent. of carbon, were heated to temperatures varying from 75°o C. to II5 o° C. and quenched, either in water or in a lead-tin bath, at 3oo ° C. Quenching at the higher temperature gave the highest tenacity. The tabulated results of the mechanical tests of hardened steels, after tempering in rape oil at temperatures from Ioo ° C. to 65°o C., show that it is not possible to obtain the same results by direct quenching in oil or in a lead-tin bath as by quenching in water and subsequently tempering. To determine the influence of time on tempering---~.e., whether heating at 5oo ° C. for a few seconds would produce the same structure as heating at Ioo ° C. for many hours---~pieces of steel containing o.87 per cent. of carbon were heated to varying temperatures for different periods of time, and then examined for
CURRENT ToPIcs.
97
scratch hardness, loss of weight in a I per cent. acid solution, the amount of carbide, and microscopically. It is concluded that hardened steel always tends to change into a-iron and free cementite. Although this change proceeds imperceptibly at ordinary temperatures, it takes only a few seconds at 65 °0 C. and some hours at IOO° C.
Silver, Tin, Lead: the Ternary System.
N. PARRAVANO.
(Ga~. Chim. Ital., xli, 813.)--This paper is a thermal and microscopic study of ternary alloys of silver, tin, and lead. All the ternary alloys are composed of the four solid phases, mixed crystals of silver and tin, mixed crystals of lead and tin, the compound Ag3Sn, and crystals of tin. The system contains two non-variant points, one of which, at about 3oo ° C., is a transformation point, while the other, at about 175 ° C., is an eutectic point. The ternary eutectic contains 63.4 per cent. of tin, 35.6 per cent. of lead, and I per cent. of silver. The transformation point is very near the binary lead-silver eutectic point, and the ternary eutectie point is very near the binary tin-lead eutectie point. This paper has 23 microphotographs.
Paper Pulp from Eucalyptus. ANon. (Paper Making, xxx, 376.)mSamples of pulp of excellent quality have been prepared from the eucalyptus (blue gum) which has been planted over large areas in Southern California. The pulp is strong, clean, and slightly reddish, owing to the action of the alkali. Experiments with this wood as a raw material for paper pulp have been carried out at Washington and leave no doubt that it is suitable for the purpose. A sufficient growth of blue gum may be obtained in four to six years; three years after cutting the stump yields a further good growth. Preservative Treatment of Poles. W . H . KEMPFER. (Forest Service Bull., 84, I 9 I I . ) - - A s the pressure method of treatmenl~ with creosote is comparatively costly, investigations were directed to simpler and cheaper methods, which could be employed locally. Special attention was given to the seasoning of the timber, and investigations were conducted with the object of ( I ) testing the efficiency of various wood preservatives and of the application of varying amounts; (2) developing a method for impregnating the butt, as the portion of the pole most subject to decay; (3) designing inexpensive apparatus for local use in application. The timbers used were chestnut, three kinds of cedar, and three kinds of pine; and six different commercial preservatives were tried. The conclusions reached were: The reduction in the weight of poles by seasoning is generally from 16 to 3° per cent., and thorough seasoning is an essential preliminary to preservative treatment. Poles cut during autumn and winter lose weight less rapidly but more