Volume 1

A manual of chemistry / by William Thomas Brande.

  • William Thomas Brande
Date:
1848
Catalogue details

Licence: Public Domain Mark

Credit: A manual of chemistry / by William Thomas Brande. Source: Wellcome Collection.

Provider: This material has been provided by King’s College London. The original may be consulted at King’s College London.

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    before that body, in consequence of a letter received from Mr. Musgrave, of Oxford. “ Dr. Croune said, lie had observed water put into a bolt- head rise higher before freezing. Mr. Hooke attributed this to the shrinking of the glass. Dr. C. said, the glass had been long in the cold before, and the water rose immediately. Dr. Wallis proposed that an emptv glass might he well cooled in a freezing liquor, in order that it might have its contraction before the water be put into it. This was done immediately by Mr. Hunt, and the water being put into a small bolt-head rose in the neck.” Numerous and correct experiments have completely established this peculiarity in the freezing of water; other fluids have their maximum of density just before the freezing-point; water expands before it freezes, and consequently water at 36° is lighter than water at 40°, and floats upon its surface; hence it is, that large masses of water, being cooled by the atmosphere upon their surface, only freeze there, and the water beneath retains the more congenial temperature of 40°. Among the experiments made by the Acccidemia del Cimenlo, we find many details independent of those already adverted to, which are at once accurate and curious, and especially in that section of their Transactions, entitled Experiments relating to Ice. In the sixth experiment of this section, they notice the effect of various metallic vessels upon the thawing of ice: they found it was longer preserved in lead and tin, than in similar vessels of brass and of iron; and that it soon thawed in gold, and sooner in silver. This enumeration of the metals is in the order of their con- ducting power, as ascertained more than a century afterwards by Dr. Ingenhousz. The radiation, reflection, and refraction of heat, are subjects of inquiry which] also probably engaged much of the attention of the Florentine experimentalists, but their published essays contain scarcely any details relating to them. In the ninth experiment, however, of the above quoted section, they have given an account of a discovery that afterwards excited much discussion, relating to the reflection and radiation of cold. “ We were anxious to try if a concave mirror, placed before a mass of ice, weighing five hundred pounds, caused any reflection of cold upon a very delicate thermometer placed in its focus; and truly it began immediately to fall; but in consequence of the vicinity of the ice, it was doubtful whether the effect resulted from the direct, or from the reflected rays; we, therefore, covered the mirror, and whatever was the cause, certain it is that the spirit began immediately to rise again. With all this, we do not mean positively to affirm that no other cause could have produced such an effect, than the absence of the rays reflected from the mirror, for we were not careful in adopting all the precautions requisite in such an experiment*.” giudizio dezli occhi, affatto priva di mo- in instanti ledecine ole decine de’grndi.” vimento. Poi a poco a poco si vedea Esperienze intorno at proyresso deyli arti- ricominciare a salire, ma con tin moto Jiziuli ayyhiaeciamenti, e <le’ loro mirabili tardissimo, e apparentemente equabile, accidenti. Saggi di natural! espcrienzo dal quale senz’ alcun proporzionale ac- fatte nell’ accademia Del Cimento. Fi- celeramento spiccava in un subito un renze, I ft1.) 1. furiosissimo salto, nel qtial tempo era * Stiyyi, above quoted. ScoalsoWal- impossibile tenerle dietro coll’ occhio, ler’s Translation of the Essays of the scorrendo con quell’irnpeto, per cost dire, Academicians del Cimenlo. 1084.