Table Of ContentImperial German Standards
Commission
Tables for Ascertaining
the Density of American
Mineral-Oils and their
products by means of
the Thermo-Areometer.
TABLES
for ascertaining
the Density of American Mineral-Oils
and their products
by means of the
Thermo-Areometer.
IMPERIAL GERMAN STANDARDS COMMISSION.
Springer-Verlag Berlin Heidelberg GmbH
1893
ISBN 978-3-662-33441-6 ISBN 978-3-662-33838-4 (eBook)
DOI 10.1007/978-3-662-33838-4
l'rintcd by H. S. Hermann, Berlin.
I NTRODUCTION.
§ 1.
Apparent and true density, application of table I.
1. The areometer (or hydrometer) serves for ascertainiug
the density (or specific gravity) of liquids, the unit of the scale
indications being the density of pure water in its most contracted
state (4 o Celsius about) under normal conditions.
2. When the instrument would have always the same
temperature, it would indicate immediately the true density of
a liquid. But "since this will not be the case, and since the
rise or fall of the temperature is followed by an expansion or
contraction of the volume of the instrument, the areometer
indicates comparatively a greater density for higher tempe
ratures, so that its indications are not true but at one fixed
temperature.
This fixed temperature, to which the areometer is adjusted,
is termed the Standard-Temperature of the areometer;
at this temperature its indications represent true densities, at all
other temperatures they give only apparent densities. Hence
generally the areometer does not indicate the true density, unless
its readings be corrected by numbers varying with the deviation
from the standiud-temperature.
3. Liquids having too, even maintaining the same weight,
different volumes at different temperatures, their densities vary
with the temperature, so that in comparing densities the tem
perature must be the same in different cases. For that purpose
a special temperature has likewise been established as the
Standard-Temperature of the liquids. But to establish
that standard-temperature in all particular cases would be a
tedious task and would create a source for errors. Hence, as
in the former case, an improved method of reckoning has been
IV
adopted, furnishing the means for reducing the densities observed
at other temperatures into such at the standard-temperature of
+
the liquids. For that standard-temperature in these tables 15°
of the Celsius-scale (59 ° F.) is adopted. The standard-tempe
+
rature of the instrument, being equally established at 15 ° C.,
the two reductions, for temperature of the instrument and · for
that of the liquid, are combined and shown in table 1. As
there may be, particularly in working, desirable to know like
wise the true densities at any other temperature, a second table,
table 2, containing these densities is added.
From the preceding it follows, that the reading of the areo
meter-scale must be supplied by readings for temperature; forthat
purpose the areometer is provided with a thermometer, constituting
in this combination the so called thermo-areometer.
4. Table 1 :for obtaining the true density at standard
temperature gives for every temperature read and every density
read the true density at '-t 15 o C., including all densities
between 0,620 and 0,920 and progressing in units of the third
decimal. For all densities read up to 0,840 the true densities
are calculated to 0,0005, for densities above 0,840 only to 0,001.
Both the starting-point and the terminus of the thermometer-scale
on the thermo-areometer, were fixed at one band to meet the
requirements of practical use and on the other band with regard
to the boiling as weil as freezing point of mineral-oils. Forthis
reason for densities not greater then 0,840 the temperatures
+
run generally from - 10 ° C. to 35 °, advancing in half
degrees, but cease for lighter oils boiling at temperatures below
+ 35 ° under + 35 ° and begirr for heavier oils at temperatures
lügher then - 10°, because some of them show a tendency to
obstructing turbidness already at 0°. For densities higher then
0,840 the temperatures rise in whole degrees and extend from
+ c.
0° or +5° up to 60°
5. On each page of the table the apparent densities read
on the areometer are quoted on the cross-top-line, the tempe
ratures read are given in the first longitudinal column; the ten
+
columns following show the true densities at 15° C., referring
to the densities read and quoted on the cross-top-line and to
the temperatures read and given in the first column. To ten
densities two pages are allotted, the numbers for lower tempe
ratures being on the one page, that for higher temperatures on
the other one. For readings of higher precision, as for those in
four decimals of the density or in tenths of a degree the true
V
densities will be found by means of interpolation under the
customary rules.
6. Table 2, showing the true densities of mineral-oils at
+
temperatures above 15 ° C., contains to all true densities at
the standard-temperature + 15° C. (to be taken from the table 1
according to the readings of the two scales on the thermo
areometer) the true densities at all temperatures between + 15°
and + 60 ° C. The arrangement is similar to that of table 1,
with the exception that in place of the apparent densities the
true densities at + 15° are quoted and in place of the latter the
true densities at the other temperatures are given.
To further illustrate the use of both tables, one may have
read in a mineral-oil on the ateometer-scale of a thermo-areo
meter an apparent density of 0,8203, on the thermometer-scale
+ +
a temperature of 18,5 ° C.; find the true density at 27,5 ° C.
Take from table 1 by means of interpolation for true density at
+ +
15° C. 0,8228 and from table 2 for true density at 27,5°
likewise by means of interpolation 0,8140.
7. The tables are calculated from experiments on the
thermal expansion of American mineral-oils and their products
made by the Imperial German Standards Commission. But as thP
expansion of oils from different countrieswill not generally be the
same, the tables give the true numbers only for American oils; but
the numbers for Russian oils differing only by 1 or 2 units of the
third decimal, while those of German oils find their place between
the numbers for American and those for Russian mineral-oils,
the tables may also be used for Russian and German oils and,
as a rule, will furnish in most cases sufficiently accurate figures.
The decimals given answer all practical purposes; but the
experiments carried out by the Imperial German Standards
Commission are conducted also with due regard for scientific
researches and the highest accurary desirable.
§ 2.
Reading the Thermo-Areometer.
1. Pour the oil, of which the density is to be ascertained,
in a glass-vessel of cylindrical shape, enough transparent and
free from streaks, with a diameter of at least twice the size of
the thermo-areometer. The glass is filled up to such a height, that
-VI
the surface of the liquid remains some centimeters beneath the
edge, even when the areometer is put in.
Waite, stirring the oil in the vessel repeatedly, till its
temperature nearly coincides with that of the surrounding air.
Then clean the areometer and sink it slowly into the liquid,
avoiding all shaking and not immersing deeper than necessary.
The reading is taken at the line, where the surface of
the liquid intersects with · the beam of the areometer. The
distinguishing of this line is rendered difficult on account of the
liquid torus, shown in fig. A, which is formed araund the beam
A. B.
J
by capillary attraction. But on looking at the beam immediately
beneath the surface of the liquid a sharp line appears at the
place, above which the torus is formed, projecting to the two
sides of the beam. This line, shown in fig. B, is the line of
reading. It appears not as a line, but as an ellipsoidal surface,
\Vhen the eye of the observer is to low beneath the surface of
the liquid, but it contracts to a sharp line, as the eye is raised.
The reading of the areometer-scale must be quickly
followed by the read~ng of the thermometer-scale. For these
readings in most cases those of the next divisions may be taken,
for greater accuracy interpolate between the readings of the
two neighbouring marks, chosing as interval for comparison on
VII
the areometer-scale the next interval below. The estimated part
of the interval is to be subtracted from the reading on the
areometer-scale and added to the reading on the thermometer
scale.
2. Dark oils prevent the distinguishing of the inter
section - line on the liquid surface; in such cases the reading
must be effected in that point of the areometer-scale, where the
torus seames to cease on the beam. But as all thermo-areometers,
adjusted in Germany, give without any exception true densities;
when read in Ievel with the surface of the liquid, a correction
rnust be added for the hight of the torus. The German instru
ments have for the length of an interval hetween two marks of
the areometer-scale about 1% millimetres and for diameter of
the beam 5 to 7 millimetres; for these instruments this correction
to be added to the readings is, with an accuracy sufficient for
all practical use, 0,001 . The effect of the nature of the oil and
that of the thickness of the beam is to slight to be taken in
account and may be neglected for practical purpose.
As to the thermometer-scale, which equally cannot be read
in dark oils, approach the instrument to the wall of the glass,
till the scale of the thermometer and the mercurial column
appear, or draw the instrument out of the liquid, till the end of
that mercurial column can be seen.
For testing dark oils metallic cylinders answer the same
purpose as glass-cylinders, but then the thermometer cannot be
read, unless drawn out of the liquid in the manner just described.
3. The scales of the thermo-areometers, being printed on
paper-strips, pasted on the inner wall of the instruments, will
occasionally get loose. On the thermometer the loosening of the
scale may be stated by putting the instrument in melting snow
or in shaved ice; if the scale has retained its original place, the
largest deviation from the zero-point should not exceed 0,2 or
0,4 of a degree, according as the thermometer-scale is divided
in whole or in half degrees.
On the areometer-beam a line is engraved coinciding with
the edge of the scale, by means of this line the shifting of the
scale from loosening may be immediately perceived.
Another kind of changes in paper-scales arise from the
thermal expansion and from the contraction of paper by loosing
its humidity in high temperatures, or from other causes not
known hitherto exactly. These changes may be neglected for
temperatures not higher than 60° C., but they grow with the
- VIII
nsmg temperature to a considerable extent, lasting wholly or
partly, even after the temperature has reached low degrees.
To prevent such changes, first the capillary · tube of the
thermometer of the German areometer, is shortened not to
allow a higher heating than 70° C. Secondly there is for
greater security on the beam another line engraved immediately
beneath the lowest mark of the areometer -scale. The scale
pasted at its top shifts from that line in contracting, so that any
change may be t;asily perceived and, by measuring the distance
of the lowest mark from that line, may be taken in account as
a need correction, gradually diminishing, as the readings are
higher on · the scale and ceasing for the highest mark.
As to the thermometer-scale similar precautions are not
taken, partly for the unsignificance of the influence of such
changes on the density calculated, partly because there is not
any difficulty of stating the changes by determining the place
of the zero-point in the manner described above.
