Lectures on chemistry, including its applications in the arts

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22. oldal - It purifies it by distillation, when it raises it in vapours, and lets it fall in rain; and farther still by filtration, when, keeping it fluid, it suffers that rain to percolate the earth. We knew before that putrid animal substances were converted into sweet vegetables, when mixed with the earth, and applied as manure; and now, it seems, that the same...
20. oldal - But having afterwards procured a lens of twelve inches diameter and twenty inches focal distance, I proceeded with great alacrity to examine by the help of it what kind of air a great variety of substances, natural and factitious, would yield...
15. oldal - I do not here consider. What I call attraction may be performed by impulse, or by some other means unknown to me. I use that Word here to signify only in general any Force by which Bodies tend towards one another, whatsoever be the Cause.
347. oldal - ... and at last I arrived at the conclusion that a metallic tissue, however thin and fine, of which the apertures filled more space than the cooling surface, so as to be permeable to air and light, offered a perfect barrier to explosion, from the force being divided between, and the heat communicated to an immense number of surfaces.
184. oldal - ... each. The electric spark having passed through them, the flask became hot, and was cooled by exposing it to the common air of the room : it was then hung up again to the balance, and a loss of weight was always found, but not constantly the same ; upon an average it was two grains." He goes on to say, " I have fired air in glass vessels since I saw you (Dr. Priestley) venture to do it, and I have observed, as you did, that, though the glass was clean and dry before, yet, after firing the air,...
211. oldal - The land is cultivated without the importation of any foreign substance containing nitrogen. Now, the products of this farm must be exchanged every year for money, and other necessaries of life, for bodies therefore which contain no nitrogen. A certain proportion of nitrogen is exported with corn and cattle ; and this exportation takes place every year, without the smallest compensation ; yet after a given number of years, the quantity of nitrogen will be found to have increased. Whence, we may ask,...
20. oldal - ... of sulphur; but as I had got nothing like this remarkable appearance from any kind of air besides this particular modification of nitrous air, and I knew no nitrous acid was used in the preparation of mercurius calcinatus, I was utterly at a loss how to account for it.
183. oldal - ... that the latter are contained in it in a latent state, so as not to be sensible to the thermometer or to the eye ; and if light be only a modification of heat, or a circumstance attending it, or a component part of the inflammable air, then pure or dephlogisticated air is composed of water deprived of its phlogiston, and united to elementary heat?
184. oldal - After stating his mode of mixing the airs, and of adjusting the balance, he says, he " always accurately balanced the flask of common air, then found the difference of weight after the inflammable air was introduced, that he might be certain he had confined the proper proportion of each. The electric spark having passed through them, the flask became hot, and was cooled by exposing it to the common air of the room : it was then hung up again to the balance, and a loss of weight was always found,...
347. oldal - In exploding a mixture of 1 part of gas from the distillation of coal, and 8 parts of air in a tube of a quarter of an inch in diameter, and a foot long, more than a second was required before the flame reached from one end of the tube to the other ; and...

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