Note 9 — Chapter I · ON WATER AND ITS COMPOUNDS
George Kamensky translation
Taking the generally-accepted specific gravity of water at its greatest density—i.e. at 4° as one—it has been shown by experiment that the specific gravity of water at different temperatures is as follows:
At 0° 0·99987 At 30° 0·99574
„ +10° 0·99974 „ 40° 0·99233
„ 15° 0·99915 „ 50° 0·98817
„ 20° 0·99827 „ 100° 0·95859
A comparison of all the data at present known shows that the variation of the specific gravity St with the temperature t (determined by the mercurial thermometer) maybe expressed (Mendeléeff 1891) by the formula
St = 1 - (t - 4)2 / (94·1 + t) (703·51 - t) 1·9
t° C. according to the mercurial thermometer Sp. gr. St (at 4° = 1,000,000) Variation of sp. gr. with a rise of Volume taking vol. at 4° = 1
Temp. per 1° C. or ds/dt Pressure per 1 atmosphere or ds/dp
-10 998,281 +264 +54 1,001,722
0 999,873 +65 +50 1,000,127
10 999,738 -85 +47 1,000,262
20 998,272 -203 +45 1,001,731
30 995,743 -299 +43 1,004,276
50 988,174 -450 +40 1,011,967
70 977,948 -569 +39 1,022,549
90 965,537 -670 +41 1,035,692
100 958,595 -718 +42 1,043,194
120 943,814 -819 +43 1,060,093
160 907,263 -995 +55 1,102,216
200 863,473 -1,200 +73 1,158,114
If the temperature be determined by the hydrogen thermometer, whose indications between 0° and 100° are slightly lower than the mercurial (for example, about 0·1° C. at 20°), then a slightly smaller sp. gr. will be obtained for a given t. Thus Chappuis (1892) obtained 0·998233 for 20°. Water at 4° is taken as the basis for reducing measures of length to measures of weight and volume. The metric, decimal, system of measures of weights and volumes is generally employed in science. The starting point of this system is the metre (39·37 inches) divided into decimetres (= 0·1 metre), centimetres (= 0·01 metre), millimetres (= 0·001 metre), and micrometres (= one millionth of a metre). A cubic decimetre is called a litre, and is used for the measurement of volumes. The weight of a litre of water at 4° in a vacuum is called a kilogram. One thousandth part of a kilogram of water weighs one gram. It is divided into decigrams, centigrams, and milligrams (= 0·001 gram). An English pound equals 453·59 grams. The great advantage of this system is that it is a decimal one, and that it is universally adopted in science and in most international relations. All the measures cited in this work are metrical. The units most often used in science are:—Of length, the centimetre; of weight, the gram; of time, the second; of temperature, the degree Celsius or Centigrade. According to the most trustworthy determinations (Kupfer in Russia 1841, and Chaney in England 1892), the weight of a c. dcm. of water at 4° in vacuo is about 999·9 grms. For ordinary purposes the weight of a c. dcg. may be taken as equal to a kg. Hence the litre (determined by the weight of water it holds) is slightly greater than a cubic decimetre.