New experiments on building materials, in reference to their conducting power, dryness, & resistance to the progress of fire : as read before the Chemical Society of London / by John Hutchinson.

  • John Hutchinson
Date:
1843
Catalogue details

Licence: Public Domain Mark

Credit: New experiments on building materials, in reference to their conducting power, dryness, & resistance to the progress of fire : as read before the Chemical Society of London / by John Hutchinson. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    hours 38' and 48. I feel totally at a loss to account for this remarkable circumstance, nevertheless it is a fact, for I proved it again and again. I spent months in cooling these 24 cuboids of different substances, and I could not even obtain an approximation of result until I discovered this curious law. Shoidd the thermometer break (as oftened happened with me) the whole series of experiments must be again commenced. We must in fact consider every thermometer as a standard. At the end of table VII., I affix the result of observations with a thermometer whose bulb was rather smaller than that of the one which was used in the experiments, the results of which form the basis of these calculations. It appears to me that nothing here makes the remarkable difference of time in cooling, but the variation in the size of the two bulbs of the thermometers. There is one exception to the difference of cooling, in the cuboid of lath and plaster; the different bulbs cause only a variation of one minute and a half, but this may be in some measure accounted for, as I could not make the desired contact with the bulb and the cuboid. Mercurial contact was impossible. Hence in this case all other required circumstances were not similar. This may throw some light upon the subject. The more accurately the bulb of the thermometer fits the hole for its reception in the substance to be examined, the better will the difference of time in cooling be made apparent, and the more definite will be the experiment. Table VIII. presents the calculations of the quantity of heat conveyed compared with fir-wood and slate and cor- rected for specific heat; if common brick be taken for an example, the specific heats having been obtained from a former table; to find the heat passing in 68'.5, this being the time the fir-wood (a standard) took to cool, it will be thus stated— Cooling of Stock Brick. Cooling of Fir-wood. Specific Heat of equal bulk. Heat passing in GS'. 5 as, 75'. 75 68'. 5 .3105 .3079 To obtain the heat “conveyed outwards compared with fir-wood”— Specific Heat of equal bulk. Fir. Ilcat passing in 03'. 5 Fir-wood. Heat conveyed,” &c. as> -2205 .3079 .100 139.63 and in comparing with slate, it is scarcely necessary to add that the cooling of the slate cuboid must be substituted for that of the fir-wood. It will be observed in table VII., that the was very uniform; but if there is much, variation phene pressure, the laws of cooling, I have reason barometer of atmos- to believe,
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