Evidently, if a kilogram sits around doing nothing for too long, it begins to lose weight. Or rather, mass. The 118-year-old cylinder that is the international standard for the metric mass, kept tightly under lock and key outside
Made of a platinum-iridium alloy, the cylinder was cast in 1889 and measures 1.54 inches in height and diameter. Of course, it has lost mass only in relation to the 80 or so reference kilograms that exist around the world. It could be that, locked away as it's been for over a hundred years, it has remained the same and the others have gained weight.
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Introduction The colour formed when stainless steel is heated, either in a furnace application or in the heat affected zone of welds, is dependent on several factors that are related to the oxidation resistance of the steel. The heat tint or temper colour formed is caused by the progressive thickening of the surface oxide layer and so, as temperature is increased, the colours change. Oxidation resistance of stainless steels However, there are several factors that affect the degree of colour change and so there is no a single table of colour and temperature that represents all cases. The colours formed can only be used as an indication of the temperature to which the steel has been heated. Factors affecting the heat tint colours formed Steel composition The chromium content is the most important single factor affecting oxidation resistance. The higher the chromium, the more heat resistant the steel and so the development of the heat tint colou...
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