A bushel of English coal weighs 80 pounds: of Virginia coal, 93 pounds;
of Pictou, 76 pounds; of Cumberland, 84 pounds; of red ash, hard, 84
pounds.
Crude saltpetre, refined, loses nine per cent.
Chemists estimate that one hundred pounds of pearlash contain thirty
per cent. carbonic acid. In refining, it loses on the average fifteen
per cent. in weight.
Phosphate of soda brightens glass.
Borax brightens, but hardens glass.
Twenty-five silver dollars refined will give thirty-seven ounces of
nitrate of silver.
A square foot of furnace clay weighs one hundred and twenty pounds.
Alum, calcined, loses in weight sixty per cent.
Crude flint batch, melted and ladled out, loses in the average fifteen
per cent. in weight.
Hard coal will measure forty cubic feet to a gross ton.
Glass in water. There are some peculiar phenomena connected with hot
glass and water. If a ball of red-hot iron is placed in a vessel
containing cold water, the latter is quickly agitated. But a ball of
melted glass of equal weight dropped in cold water will produce no
immediate agitation. The water will remain for some time quiescent; but
when the glass is cooled to about half its highest temperature, it
agitates the cold water violently.
Technical terms, descriptive of glass, such as crystal, flint, tale,
may be derived from these facts: the French used for their base crystal
stones, burnt and ground fine; in England they had recourse only to
flint stone, treated the same as the French used their blocks of
crystal; tale was derived from the mode of selling, the best glass
being sold only by weight, while light articles were sold tale.
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