A dictionary of materia medica and practical pharmacy; including a translation of the formulæ of the London pharmacopœia / By William Thomas Brande.

  • Brande, William Thomas, 1788-1866.
Date:
1839
Catalogue details

Licence: Public Domain Mark

Credit: A dictionary of materia medica and practical pharmacy; including a translation of the formulæ of the London pharmacopœia / By William Thomas Brande. Source: Wellcome Collection.

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    TABLE IV. TEMPERATURE is in all cases specified in the language of Fahrenheit’s thermometric scale, in which the freezing point of water is marked 32°, and the boiling point 212°; the space between these two points being divided into 180 equal parts or degrees. The graduation proceeds downwards to 0° or zero, which is the lowest temperature to be obtained from a mixture of snow and salt, and 32° below the freezing point of water, or what amounts precisely to the same thing, below the point at which ice begins to thaw. The graduation is then carried on below zero, in the same way as above. In France, Sweden, and many other parts of Europe, the Centigrade thermometric scale, originally used by Celsius in Sweden, is employed, in which the freezing point of water is marked 0°, and the boiling point 100°. In Italy, and in many parts of Germany and elsewhere, a third thermometric scale is used, namely, that of Reawmur, in which the freezing point of water being marked 0°, the boiling point is marked 80°. To distinguish, in each of these thermometers, the degrees above 0° from those below 0°, the mark + or plus is frequently annexed to the former, and the mark — or minus to the latter; but when the degree is merely stated without prefix or remark, it is generally understood, especially with us, as referring to the degrees above zero. ; The temperature, as expressed by one thermometer, may be reduced to that of either of the others, by knowing the relation which subsists between their respective degrees. Thus 180°, (the number of degrees between the freezing and the boiling points of water on Fahrenheit’s scale,) is to 100° (the number of degrees between the freezing and boiling points on the Centigrade scale) as 9 to 5; and to 80° (the number of degrees between the freezing and boiling points on Reaumur’s scale) as9 to 4. Nine degrees, therefore, of Fahrenheit are equal to five of the Centigrade, and to four of Reaumutr’s scale. Hence Fahren- heit’s degrees are reduced to those of the Centigrade by multiplying by 5 and dividing by 9, or to those of Reaumur by multiplying by 4 and dividing by 9. On the other hand, by reversing this process, the degrees of the Centigrade and of Reaumur are reduced to those of Fahrenheit, the multiplier being then 9, and the divisor 5, in the one case, and 4 in the other. In these reductions it must be recollected that the zero of Fahrenheit’s thermometer, is 32° below that of the Centigrade and of _Reaumur, as in the following instances :— Fahrenheit. Centigrade. 68° — 32°9=— 36 x 5 = 180 +9 = 20° ee ee LOOK Oy See O00K- Di a 100 Centigrade. Fahrenheit. 1° x 9= 90+5 = 18 + 32 = 50° 100 x 9 = 900 + 5 = 180 + 32 = 212