United States or Liechtenstein ? Vote for the TOP Country of the Week !
The convinced upholder of the phlogistic theory had two answers to the argument, that, because the earth-like product of the calcination of a metal weighs more than the metal itself, therefore the metal cannot have lost something in the process; for, if one portion of what is taken away weighs more than the metal from which it has been separated, it is evident that the weight of the two portions into which the metal is said to have been divided must be considerably greater than the weight of the undivided metal.
Plastic clay is wanting in these properties; but they are imparted to it by a feeble calcination. The operation was extended to a depth of three feet. This was an expensive process, certainly; but it was effectual. The great difference in the properties of burnt and unburnt clay is illustrated by what is seen in brick houses, built in moist situations.
He demonstrated the fallaciousness of both these theories in 1768-1769 by elaborate experiments, a single investigation of this series occupying one hundred and one days. In 1771 he gave the first blow to the phlogiston theory by his experiments on the calcination of metals.
This theory fitted very nicely as applied to the calcined lead revivified by the grains of wheat, although with some other products of calcination it did not seem to apply at all. It will be seen from this that the phlogistic theory was a step towards chemistry and away from alchemy.
The product of the calcination of equal parts of lead and tin 2 parts, carbonate of soda 1 part, antimonic acid 1 part, rub together, or triturate, and melt. Litharge 18 parts, sand 4 parts, oxide of antimony 2 parts, sienna earth 2 parts; melt. If it is too deep the proportion of sienna earth may be decreased. Chromate of lead 1 part, minium 3 parts.
Unfortunately, too, it is the custom of the natives to prepare the substance for the market by an imperfect calcination, and hitherto I have only been able to study specimens procured in the markets which have been subjected to this process.
As he had obtained his dephlogisticated air by heating the calx of mercury, that is the powder produced by calcining mercury in the air, Priestley was forced to suppose that the calcination of mercury in the air must be a more complex occurrence than merely the expulsion of phlogiston from the mercury: for, if the process consisted only in the expulsion of phlogiston, how could heating what remained produce exceedingly pure ordinary air?
In preparing my improved composition I take cleaned or precipitated chalk, and subject it to the process of calcination in a suitable crucible over a clear coal or charcoal fire for three or four hours, or thereabout. I then add to the calcined chalk about one-third of its weight of sulphur, and heat the mixture for from forty-five to ninety minutes, or thereabout.
It was superficial because it overlooked the fact that the primary calcination, the mortification, of the metals, and the other substances, was effected in the air, that is to say, in contact with something different from the thing which was calcined; the explanation was of the kind which people call theoretical, when they wish to condemn an explanation and put it out of court, because it was merely a re-statement of the facts in the language of a theory which had not been deduced from the facts themselves, or from facts like those to be explained, but from what were supposed to be facts without proper investigation, and, if facts, were of a totally different kind from those to which the explanation applied; and lastly, the explanation was unworkable, because it suggested no method whereby its accuracy could be tested, no definite line of investigation which might be pursued.
By this investigation Lavoisier destroyed part of the experimental basis of alchemy, and established the one and only method by which chemical changes can be investigated; the method wherein constant use is made of the balance. Lavoisier now turned his attention to the calcination of metals, and particularly the calcination of tin.
Word Of The Day