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Dangers of coal
94
CURRENT ToPIcs.
Kambara Earth: A Decolorizing Material for Mineral Oils, Etc. K. KOBAYASHI. (J. Ind. Eng. Chem., iv, 8 9 I . ) - - K a m b a r a earth is from the Echigo province of Japan and belongs to the same class of fuller's earth as that found in Florida, but is more efficient. It resembles hard wax, feels soapy, has detergent properties, and is dissociated by and miscible with water. It consists of fine particles of earth without any admixture of quartz. Its contents are: silica 6o.71 per cent., aluminum oxide 13.18 , iron oxide 3.68, calcium oxide 0.62, magnesium oxide 0.38 , sodium and potassium oxides 1.54 , and loss on ignition 20.o4 per cent. It is essentially composed of hydrates of silicic acid and aluminum silicates. Numerous experiments on its action with dyes are recorded.. With crude petroleums it absorbs the unsaturated hydro-carbons. It removes certain impurities from methyl alcohol, and tar from pyroligneous acid. The earth is slightly acid, and is thus distinguished from ordinary kaolin and clay, and probably some of its efficiency is due to this acidity. Use of Mica as an Insulator. F. WIGGINS. (Elec. Rev., lxxi, 564.)--Mica can be obtained in sizes up to 24 inches by 12 inches. The limitations of micanite are pointed out, but the quality depends largely on the price paid. Pure mica tubes, consisting entirely of rolled mica without any cement, can be obtained up to 12 inches or 18 inches in length, and, as they can be used much thinner than the micanite tubes, the increased cost is not so large as might appear at first sight. Hints are given as to the splitting and working of mica, which requires care and experience.
Dangers of Coal.
M. DENNSTEDT and L. SCI-IAFER.
(Zeit.
Mngew. Chem., xxv, 2625.)--Commences by describing an ap-
paratus and a method by which coals may be tested and classified as regards their liability to self-ignition. Such tests would furnish definite data as to the safety or danger of storing and transporting any particular type of coals. Coals which when heated to 15o° C. in • a stream of oxygen show no tendency to increase of temperature are absolutely safe; those which show a slight tendency to heat up locally but fail to ignite within an hour are safe enough for storing and transporting on board ship. Those which ignite within an hour and below 15o ° C. are relatively dangerous coals. The temperature of self-ignition, and the time of heating necessary, determine relatively the degree of danger. In general the heat value of the coal is not an index as to its tendency to self-ignition; brown coals are much more dangerous in this respect than soft coals. The presence of finely-divided particles in a coal pile increase this danger greatly. The coals tested show that the greater the percentage of oxygen in the coal the greater the liability to self-ignition.
CURRENT ToPIcs.
Kambara Earth: A Decolorizing Material for Mineral Oils, Etc. K. KOBAYASHI. (J. Ind. Eng. Chem., iv, 8 9 I . ) - - K a m b a r a earth is from the Echigo province of Japan and belongs to the same class of fuller's earth as that found in Florida, but is more efficient. It resembles hard wax, feels soapy, has detergent properties, and is dissociated by and miscible with water. It consists of fine particles of earth without any admixture of quartz. Its contents are: silica 6o.71 per cent., aluminum oxide 13.18 , iron oxide 3.68, calcium oxide 0.62, magnesium oxide 0.38 , sodium and potassium oxides 1.54 , and loss on ignition 20.o4 per cent. It is essentially composed of hydrates of silicic acid and aluminum silicates. Numerous experiments on its action with dyes are recorded.. With crude petroleums it absorbs the unsaturated hydro-carbons. It removes certain impurities from methyl alcohol, and tar from pyroligneous acid. The earth is slightly acid, and is thus distinguished from ordinary kaolin and clay, and probably some of its efficiency is due to this acidity. Use of Mica as an Insulator. F. WIGGINS. (Elec. Rev., lxxi, 564.)--Mica can be obtained in sizes up to 24 inches by 12 inches. The limitations of micanite are pointed out, but the quality depends largely on the price paid. Pure mica tubes, consisting entirely of rolled mica without any cement, can be obtained up to 12 inches or 18 inches in length, and, as they can be used much thinner than the micanite tubes, the increased cost is not so large as might appear at first sight. Hints are given as to the splitting and working of mica, which requires care and experience.
Dangers of Coal.
M. DENNSTEDT and L. SCI-IAFER.
(Zeit.
Mngew. Chem., xxv, 2625.)--Commences by describing an ap-
paratus and a method by which coals may be tested and classified as regards their liability to self-ignition. Such tests would furnish definite data as to the safety or danger of storing and transporting any particular type of coals. Coals which when heated to 15o° C. in • a stream of oxygen show no tendency to increase of temperature are absolutely safe; those which show a slight tendency to heat up locally but fail to ignite within an hour are safe enough for storing and transporting on board ship. Those which ignite within an hour and below 15o ° C. are relatively dangerous coals. The temperature of self-ignition, and the time of heating necessary, determine relatively the degree of danger. In general the heat value of the coal is not an index as to its tendency to self-ignition; brown coals are much more dangerous in this respect than soft coals. The presence of finely-divided particles in a coal pile increase this danger greatly. The coals tested show that the greater the percentage of oxygen in the coal the greater the liability to self-ignition.