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preface to fifteenth edition

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2.66 SECTION 2<br />

2.1.1 Conversion of Thermometer Scales<br />

The following abbreviations are used: F, degrees Fahrenheit; C, degrees Celsius; K, degrees<br />

Kelvin; Ré, degrees Reaumur; R, degrees Rankine; Z, degrees on any scale; (fp)“Z”, the freezing<br />

point of water on the Z scale; and (bp)“Z”, the boiling point of water on the Z scale. Reference:<br />

Dodds, Chemical and Metallurgical Engineering 38:476 (1931).<br />

F 32 C Ré K 273 R 492 Z (fp)“Z”<br />

<br />

180 100 80 100 180 (bp)“Z” (fp)“Z”<br />

Examples<br />

(1) To find the Fahrenheit temperature corresponding <strong>to</strong> 20C:<br />

F 32 C F 32 20<br />

or <br />

180 100 180 100<br />

(20)(180)<br />

F 32 <br />

36<br />

100<br />

F 4<br />

(2) To find the Reaumur temperature corresponding <strong>to</strong> 20F:<br />

F 32 Ré 20 32 Ré<br />

<br />

180 80 180 80<br />

i.e.,<br />

20F 5.33Ré<br />

(3) To find the correct temperature on a thermometer reading 80C and that shows a reading of<br />

0.30C in a melting ice/water mixture and 99.0C in steam at 760 mm pressure of mercury:<br />

C Z (fp)“Z” 80 (0.30)<br />

<br />

<br />

100 (bp)“Z” (fp)“Z” 99.0 (0.30)<br />

i.e., C 80.87 (corrected)<br />

2.1.2 Density and Specific Gravity<br />

2.1.2.1 Hydrometers. Various hydrometers and the relation between the various scales.<br />

Alcoholometer. This hydrometer is used in determining the density of aqueous ethylalcohol<br />

solutions; the reading in degrees is numerically the same as the percentage of alcohol by volume.<br />

The scale known as Tralle gives the percentage by volume. Wine and Must hydrometer relations<br />

are given below.<br />

Ammoniameter. This hydrometer, employed in finding the density of aqueous ammonia solutions,<br />

has a scale graduated in equal divisions from 0 <strong>to</strong> 40. To convert the reading <strong>to</strong> specific<br />

gravity multiply by 3 and subtract the resulting number from 1000.<br />

Balling Hydrometer. See under Saccharometers.<br />

Barkometer or Barktrometer. This hydrometer, which is used in determining the density of<br />

tanning liquors, has a scale from 0 <strong>to</strong> 80 Bk; the number <strong>to</strong> the right of the decimalpoint of a<br />

specific gravity reading is the corresponding Bk degree; thus, a specific gravity of 1.015 is<br />

15 Bk.

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