STAS 35-81 R

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ICS 75.080

ROMANIAN STANDARD STAS 35-81

Classification index A 51

Replacing:

STAS 35-73

Previous editions:

1950;1958,1973;1980

CRUDE, OIL LIQUID SEMI-LIQUID AND SOLID PETROLEUMPRODUCTS

Determination of density!I!EI, PRODUSE PETROLIERE LICHIDE, SEMISOLIDE "I SOLIDE

Determinarea densit#$iiPETROLE BRUT, PRODUITS PETROLIERES LIQUIDES,

SEMISOLIDES ET SOLIDES

Determination de la densite

Validation date:

1981-04-01

1. GENERAL

1.1 Scope

This standard establishes the determination methods of density of crude petroleum, liquid petroleum products,semi-solid petroleum products (bitumen, paraffin jelly) and solid (parafinne, ceresine parafinne, petroleum butter, ceres,

etc.). The standard is not applied in determination of density of very volatile liquids, which have vapors pressure above

1.8 bars (180 kPa), determined, according to STAS 121-80, as well as for petroleum coke.

The density is determined according to the following methods:

- method with the areometer (the densimeter);- method with the hydrostatic balance (Mohr Westphal);- method with the density bottle.The method used is indicated in the product standard.

1.2. Definitions

1.2.1. The density of a body is the determined mass in vacuum and reported to its volume, at the temperature of 150C or 20 0C. Density is expressed in kg/m3.NOTE In this standard density is expressed in g/cm

3(1 g/cm

3= 10

3kg/m

3).

Density is symbolized by %20

or %15

.

1.2.2. Relative density is the ratio between the density of a body at the temperature t 0C and the density of an equalvolume of pure water at the temperature t1

0C. In our country temperatures of 15

0C or 20

0C are used.

The relative density is a dimensionless number.

The relative density is symbolized by dtt1, respectively d

20

20 , d15

15 , d20

4 or d15

4 , and the last symbols have the

value of relative density identical to the one of density at respective temperatures

2. DETERMINATION OF DENSITY WITH THE AREOMETER (DENSIMETER)

2.1. The principle of the method

The sample is poured in a cylinder which has a temperature approximately equal to the one of the sample.

Depending on the estimated density of the sample an areometer is chosen with the scale graduated conveniently, which

is introduced in the sample cylinder and is let to float. When the equilibrium of temperature is reached, the value of the

density on the graduated scale of the bar is read as well as the temperature of the sample.

2.2. EquipmentAreometers (fig. 1) which fulfil the requirements established in STAS 7985-67, with the reading accuracy of 0.0005

g/cm3

.

ASOCIA!IA DE STANDARDIZARE DIN ROMNIA (ASRO),Adresa po&tal#: str. Mendeleev 21-25, 70168, Bucure&ti 1, Direc$ia General#: Tel.: +40 1 211.32.96; Fax: +40 1 210.08.33,

Direc$ia Standardizare: Tel. : +40 1 310.43.08; +40 1 310.43.09, Fax: +40 1 315.58.70,

Direc$ia Publica$ii: Serv. Vnz#ri/Abonamente: Tel: +40 1 212.77.25, +40 1 212.79.20, +40 1 212.77.23, +40 1 312.94.88 ;

Fax : +40 1 210.25.14, +40 1 212.76.20

ASRO Entire or partial multiplication or use of this standard in any kind of publications and by any means (electronically, mechanically,photocopy, micromedia etc.) is strictly forbidden without a prior written consent of ASRO

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STAS 35-81 2

The use of aerometers equipped with inner thermometer (thermoareometers) is admitted, provided that the

indication for temperature of the respective thermometer is not supposed to be used.

- Thermometer with the value of the division of 0.5 0C. The thermometer shall have the graduated scale thuschosen as to permit the reading of the temperatures on which are worked at, in the domain of measuring

from 20 + 1020C.

- transparent or metal glass cylinder for the light-tight products. When the cylinder used is made of metal, thefact that the accurate reading at the areometer can be done only in case that the level of the sample is foundat as much as 5 mm from the superior edge of the cylinder is taken in consideration. The inner diameter of

the cylinder shall be thus chosen as to ensure the introduction of the thermometer without the areometer to

touch the walls of the cylinder. The cylinder shall have such a height that the areometer floats freely in the

sample and a distance of minimum 25 mm between its inferior side and the bottom of the cylinder.

- Bath with a constant temperature with precision of 0.2 0C which is used when the nature of the sampleneeds the determination of density at a temperature way superior or inferior to the temperature of the

environment.

2.3. Preparation of the sampleThe value of the density determined with the areometer is more precise if it is done at the temperature at which

the areometer is calibrated (reference temperature) or close to it, but it can be done at any temperature within theinterval 18 + 90

0C, depending on the sample type, with observing the conditions established by table 1.

The product is homogenized by mixing. The sample is poured into the dry and clean cylinder, maintained invertical position and brought at a temperature closed to the one chosen for determination accomplishment. The product

is poured taking care not to form foams, not to form air bubbles and not to blow water drops.

The foam, eventually formed by the air bubbles from the surface of the liquid, is broken by approaching a

heated stick made of glass or metal, without touching its surface. In case of volatile products, the filling of the cylinder

is done by siphoning. The air bubbles which could form in case of these products are eliminated by touching them with

a clean filter paper, after which the bubbles have reached the surface of the liquid.

Table 1

Sample typeDistillation initial

temperatureOther limits

Determination of

temperature

Very volatile under 1000C

vapors pressure under 1.8

bars (180 kPa)

the flask with the

sample, well closed, is

cooled up to 20C or to a

less temperature

Volatile max. 1200C -

the flask with the

sample, well closed, iscooled up to 20

0C or to

a less temperature

Volatile and heavy-bodied max. 1200C

high heavy-bodied

characteristic, at 200C

is heated at a minimum

temperature which

allows obtaining a

sufficient fluidity

Non-volatile above 1200C -

the determination is done

at any temperature up to

900C

Blending of petroleumproducts and non-

petroleum products

- - the determination is doneat 15 0.20C or to 20

0.20C

2.4.Working modality

2.4.1. The areometer, dry and clean, is slowly introduced in the sample from the cylinder placed in a verticalposition, in a room, in a place protected of air courses and heating sources. The areometer is kept by its superior part

and is introduced in the sample paying attention to the fact that the cylinder walls are not to be touched. Concomitantly

the temperature of the sample is determined by introducing the thermometer and its shaking in the sample, until thetemperature indicated by the thermometer is maintained constant. It is controlled that the temperature of the sample not

to vary with as much as 0.50C during the determination; at the same time the temperature of the environment is not to

vary with as much as 2 0C.When the determination is accomplished at temperatures net superior or inferior to the temperature of the

environment, the bath with constant temperature is used in order to avoid the too high temperature variations. In order

to avoid humectation with the sample of the superior part of the areometer bar, which is placed above the dip into liquidlevel are taken necessary precautions. The shaking of the thermometer is done continuously taking care that the mercury

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STAS 35-813

vessel tank is permanently in the sample. When the temperature indicated in the thermometer is maintained constant,

with a variation of max. 0.50C, its value is written down then the thermometer is taken from the sample.

2.4.2. The areometer is dipped into the sample with about two divisions above the level of the dipping and then is leftto get up.

In case of samples with low heavy-body content there to the areometer can be derived with a slow rotate

movement, in the moment of its liberation, thus avoiding a too much closeness of it to the interior wall of the cylinder.

After the oscillations of the areometer stopped and all the air bubbles reached the surfaces, the divisioncorresponding to the inferior meniscus of the liquid is read, keeping the eye at the same level with the liquid.

2.4.3. The value read is corrected if it corresponds to the point on the scale of the areometer where the surface of theliquid cuts it. This value is determined by placing the hand hole just a little under the level of the liquid, lifting then

slowly the eye up to the surface of the liquid, which is seen at first under the form of an deformed ellipse, which then

appears as a straight line which cuts the areometer scale.

2.4.4. In case of light-tight liquids, the reading of density is done by keeping the hand hole just a little above theplane surface of the liquid and thus reading the division of the areometer in the point up to which the liquid samplereaches. This reading done at the superior part of the meniscus needs a correction in case the areometer is not calibrated

for such a reading.

In case the correction for the areometer used is necessary, this can be determined by a transparent oil, with a

superficial stress closed with the one of the sample. The respective areometer is dipped into oil and is read on the scale

of the areometer the maximum height which it reaches above the surface of the liquid. The difference between the

superior meniscus and the surface of the liquid is written down, and the value obtained is extracted from the value of the

density read on the areometer. The following corrections can be used:

-

for areometers with the value of the division 0.0005 the correction is +0.0007- for areometers with the value of the division 0.001 the correction is +0.00142.4.5. In case of the liquids with heavy-bodied characteristic, the areometer is left in the sample enough time in orderto establish the equilibrium position, as in this case the oscillations on vertical have a less frequency and the calibrations

takes longer.

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STAS 35-81 4

2.4.6. Immediately after the reading on areometer was achieved, the sample is shaked again with the thermometer,but its mercury vessel tank is at all times dipped into the sample. The temperature of the sample is written down with a

variation of maximum 0.50C. If this temperature differs by much than 0.5

0C from the one previously read, the reading

at the thermometer and at the areometer are repeated, until the difference between the tow readings do not go over 0.50C.

NOTE If the areometer has lead particles attached with parafinne and during the determination it was heated at atemperature above 38 0C, after the accomplishment of the determination, this is left to get dropped and to becooled, keeping it in a vertical position. If the heating of the areometer is necessary, this shall be manipulated and

heated, also in a vertical position.

2.5. Calculus

2.5.1. The correction for the densities read are accomplished, in conformity with the calibration certificate of theareometer, in case this exists. Then the correction of meniscus for the value read in case of the light-tight products isaccomplished. The final value is written down with a precision of 0.0005 g/cm.

The arithmetic mean of the temperatures read at the beginning and the end of the determination expressed with

an accuracy of 0.50C.

NOTE The values read on the areometer, at different temperatures from the one of the calibration, do not represent real

values of density, as the volume of the vessel tank of the areometer varies with the temperature.

2.5.2. In order to transform the values read on the areometer (according to clause 2.5.1) in density, at 20 0C, the table7 is used, and in order to obtain the density in 15

0C the table 8 is used.

The calculus are done using all the decimals given in the tables.

2.6. Determination of the density of the petroleum products stored in vessel tanksIn order to establish the stocks of petroleum products, the density at temperature which the volume is

established is calculated using formula (1) and table 2.

The density t10C (%

t1) in g/cm

3is calculated with the formula:

!1t = !

t+ C (t t1) [g/cm

3] (1)

where:!

t density at the temperature t 0C, at which the determination was made, in g/cm3;

C correction coefficient for dilatation of the product at a temperature variation of 10C,

according to table 2, in g/cm3;

t temperature at which the determination was done,0C;

t1 temperature at which the volume from the vessel tank was established,0C.

The expression C (t t1) has a positive value if the temperature t, at which the determination was done ishigher than t1

0C and a negative value if the temperature t is less than t1

0C.

NOTE At the determination and calculus of the density in order to establish the quantity (the stock) of petroleumproducts the indications from STAS 1165-66 are observed.

If the value read on the areometer is for choosing the correction factors in order to correct the density of the

petroleum product, at the reference temperature, is recommended that the density of the product to be determined at atemperature different by as much as 30C as the temperature at which the measure of the product volume was

accomplished.

2.7. In order to determinate the density of the crude petroleum without water and impurities at the temperature atwhich the determination was done (%

tpure), the formula is applied:

p1 (100 U)

100 U!

tpure = [g/cm

3]

where

p1 the density of the crude petroleum with content (U) of water and impurities, at the temperature

at which the determination was done, in g/cm3;

U the water and impurities content of the crude petroleum after the breaking of the emulsion andthe decantation, in %.

2.8. In case of litigation, the density of the petroleum products, stored in vessel tanks, is determined at 20 0C and itis corrected at the temperature of the product from the vessel tank.

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STAS 35-815

Translation NOTE: all the values in the table written with a coma(e.g.: 0,620) are to be read with a dot (e.g. 0.620)

The coefficients are used for liquid hydrocarbon mixtures with a content of aromatic hydrocarbons under 50% volume.For aromatic hydrocarbons, the correction coefficients are the following;

- benzene oil 0.00103;- methylbenzene methane 0.00088;- xylon 0.00085.

Read density,

g/cm3

Correction coefficient for

the liquid dilatation at a

variation of temperature of

10C, g/cm

3.

0C

Read density,

g/cm3

Correction coefficient for

the liquid dilatation at a

variation of temperature of

10C, g/cm

3.

0C

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STAS 35-81 6

2.9. Allowed differencesAs a result the arithmetic mean of two determinations is taken which shall not differ between them as the

values indicated in table 3.

Table 3The product Interval of temperatures Repeatability Reproducibility

Transparent liquids with

heavy-bodied characteristicsunder 100 mm

2s

-1at 50

0C

-2 C +25C 0.0005 0.0010

Light-tight and liquids with

heavy-bodied characteristics

over 100 mm2s

-1at 50

0C

-2 C +25C 0.0010 0.0015

3. DETERMINATION OF DENSITY WITH HYDROSTATIC BALANCE (MOHR-WESTPHAL)

3.1. The principle of the method

The float bowl, hanged at the bottom of the lever of the hydrostatic balance, balanced innitially, is dipped in

the analyzed product. The lever is brought again in equilibrium status with some weight.The position of these weights indicates the density of the product.

3.2. Equipment

- Hydrostatic balance (fig. 2), composed of:- The base plate (1), with screws block constraint (2), sometime with a level indicator with air bubble;

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- a leg (3) with a fastening screw (4);- mobile bar (5) and support (6). The bar can be moved on vertical up and down and fastened with the fastening

screw (4). The support (6) is equipped with a graded scale (7) (or with a fixed indicator) and with two coverings

(8), between them being placed the pillows of the support blade;

- lever (9) with unequal arms, equipped with two blades: a double support blade (10), with the active edge down,sustained by the pillows of the support and a bearing blade (11), simple, with the active edge up, on which a hook

is placed (12). The short arm of the lever has attached in the bottom a balancing (13) and ends with an indicator

(14) which moves in front of the gradated scale (7) (or of a fix marker). The distance between the two blades ofthe long arm is divided in ten equal parts, by cuttings numbered from 1 to 9 and done in the upper part of the

arm. At some balances, instead of cuttings nine double blades are fixed;

- floating device constructed from a glass floating body (15) equipped at it upper end with a ring to which a wire isfixed from a stainless material; the other end of the wire is fixed by a hook screwed at a small metal piece (16)

equipped in its upper part with a ring or a hook. With it, the float bowl can be suspended at the balance hook. The

floating bowls ca be of 5 cm3

or of 10 cm3

and they are calibrated at 150C or 20

0C. The floating bowls are

supplied with or without the thermometers within them. The mass of the whole equipment of floating is thus

calculated as to balance the lever of the balance from air;

- glass cylinder (17) being a container for the liquid which density is being determined;- thermometer (18), with the value of the division of 0.5 0C, having the error of 0.25 0C, sustained by the

support (19).

- series of weights, made of two large weights, each mass being equal to the mass of the water volume dislocated bythe floating bowl, together with 15 20 mm wire, at the calibration temperature of the balance. The other weightsare being weighted: 1/10; 1/100 and 1/1000 from the mass of the large weight.

- pair of tweezers for manipulation of weights; the manipulation of the weights by hand is forbidden.3.3. Working modality

3.3.1. The sample is homogenized by mixing.3.3.2. the sample to be analyzed is poured in the cylinder (17), clean and dry having the temperature comprised

between 10 200C, letting it drain of a glass stick until the floating body and about 15 mm from the length of the wire

of the floating body are sunken into water. The eventual air bubbles gathered at the water surface are broken by getting

closer a glass or metal stick heated without touching the surface of the product.

It is recommended that the determination of density to be done at temperature of 200C.

In order to establish again the equilibrium of the balance, the weights are hanged one by one by the leverstarting with the heaviest weight.

After the equilibrium is established, the value indicated by the weights is read, in desiphoning sequence

according to their actual size. If at establishing again the equilibrium, there was not needed that one or several weights

to be hanged by the lever, at reading the density their place is marked with zero.

Example: In order to establish again the equilibrium, a large weight was hanged by the cutting (or the blade)of the seventh division; the second weight (1/10) was hanged by the fourth division; the third weight (1/100) was not

hanged, and the fourth weight (1/1000) was hanged by the sixth division. The density read (uncorrected) is 0.7406 at the

temperature at which the determination was done.

3.4. Calculus

As the weighting was done in air and not in vacuum conditions, and the density read (uncorrected) of the

liquid sample was influenced by the superficial stress of it, by the volume of the floating bowl and by its calibration

temperature, the density read (uncorrected) is corrected with the formula:

Density at t0C (%

t) = pn + C [g/cm

3] (2)

where

pn Density read (uncorrected) at t0C, in g/cm

3;

C Correction read from the certificate of the hydrostatic balance (which takes into consideration

the characteristics of the floating bowl and of the calibration temperature of the hydrostatic

balance) in g/cm3;

NOTE: In case the certificate of the hydrostatic balance is missing, the correction factors are used (C) from table 4.

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STAS 35-81 8

The correction factors (C), in g/cm3, corresponding to the characteristics of the floating bowl and to the

calibration temperature of the hydrostatic balance

Table 4

Translation NOTE: all the values in the table written with a coma(e.g.: 0,600) are to be read with a dot (e.g. 0.600)Example: The density of a product at 20 0C and of 15 0C is required.The density read at 18

0C (pn ) is of 0.7406 g/cm

3.

From the certificate of the hydrostatic balance is read the correction for a floating bowl of 10 cm3

and a

calibrated balance of 200C which is of 0.0010 g/cm

3.

In this case pn = 0.7406

C = - 0.0010

p018 C

= 0.7406 0.0010 = 0.7396

From table 7 is obtained pC020

= 0.7380, by interpolating between 0.730 and 0.740.

From table 8 is obtained p

C015

thus: the value 0.7380 (p

C020

) is found between 0.7379 and 0.7389 whichcorrespond to p

C015= 0.742 respectively 0.743. By interpolating is obtained p

C015= 0.7421.

3.5. Allowed differences

Repeatability: 0.0005 g/cm3.

Reproducibility: 0.0010 g/cm3

.

4. DETERMINATION OF DENSITY WITH DENSITY BOTTLE

4.1. The principle of methodThe method is based on comparison of the masses of volumes equal of sample and of water, introduced successively in

the density bottle maintained in a thermostat bath, at a certain temperature up to reaching the thermic equilibrium. Themethod is used when is needed a higher accuracy or when the other methods can not be applied.

4.2 Equipment- Density bottles (fig. 3.4 or 5) calibrated, made of glass, equipped with covers and having the volume marked

on glass. The covers have a capillary canal (fig. 3) or are equipped at their upper part with a capillary lateral

arm and with a cover with thermometer (fig. 4). Some density bottles are equipped with a marker for filling

at a certain level. The calibration of the density bottle are done at 200C. The density bottles from fig. 3 and 4

are used for liquid products with low heavy-bodied characteristics, and the one from fig. 5 for liquids with

high heavy-bodied characteristics, semi-solid products and the one frozen at the temperature of the

environment.

- Thermometer with the measurements domain from 0 30 0C, with the value of division of 0.1 0C and withmeasurement error of maximum a division.

- Thermostat, or water bath, having a depth higher than the height of the density bottle, of which temperatureis regulated with an accuracy of 0.1 0C.-

4.3 Calibration of the density bottle

Density read

g/cm

3

Factors C in /cm3

for:

Calibrated balance at

20/40C or at 15/4

0C


20/200C

Floating

bowl of 5 m3

Floating bowl

of 10 m3

Floating

bowl of 5 m3

Floating bowl

of 10 m3

Floating bowl

of 10 m3

Floating

bowl of 5 m3


15/150C

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4.3.1 Before of the determination the density bottle and its cover are cleaned with an sulfurchromic, is washed withdistilled water and then with ethyl alcohol of 96% volume, after which is dried with an air course with no dust.

The dried density bottle is kept for 30 minutes in the thermostat or in water bath, with a temperature regulated

at 20 0.10C and then is weighted (the cover being clogged on) with a precision of 0.2 mg. In case of necessity, the

electrostatic loads are annihilated blowing over the density bottle.

4.3.2 Determination of equivalent in water (the figure of the water) of the density bottleThe equivalent in water (water figure) is the mass of the distilled water at 20C contained in the density bottle clogged

with the cover and fully filled, including the capillary channel or up to the marker at the density bottles which have not

capillaries.

NOTE The equivalent in water expresses the utile volume of the density bottle at the temperature of 20 0C;

the mass of the water divided at its density at 20 0C gives the volume of the density bottle at this temperature.

With a pipette, cleaned and dried, the density bottle is filled with water freshly distilled, having the

temperature of 18 200C, paying attention not to have air bubbles, left after which it is dried at exterior with a cotton

clothing clean and dry, which does not leave fly waste, or with cellulose wadding and it is introduced clogged, in the

thermometer adjusted at 20 0.10C and is kept for 30 minutes.

NOTE After cleaning, the density bottle is manipulated with the ring of filter paper.

At the density bottles without marker, the water excess emerged from the capillary tube removed with a piece

of filter paper without touching the capillary opening, and at these with marker, the water is taken out up to the marker

using a twisted filter paper, the density bottle being kept in the thermostat.After that, the dried density bottle is weighted with a precision of 0.2 mg.

The equivalent in water (m) of the density bottle at the temperature of 200C is obtained by making the

difference between the mass of the full density bottle and that of the empty density bottle and is expressed ing.

The equivalent in water of the density bottle is verified from time to time.

4.4 Determination of density of liquid products

4.4.1 Equipment

- Density bottle according to fig. 3 or 4.NOTE Other types of density bottles can also be used, providing that same accuracy of determination is ensured.

4.4.2 Preparation of the density bottleAccording to clause 4.3.1

4.4.3 Preparation of the sampleThe sample is brought at the temperature of 18

0C. In case of products with high heavy-bodied characteristic,

the sample is heated in order to become fluid enough, but only up to the temperature of maximum 500C.

4.4.4 Working modality

The density bottle with capillary channel is completely filled with the sample that is to be analyzed, using aclean and dry pipette. The density with marker is filled with the sample a little under the marker. In order to facilitate

the separation of the air bubbles, the density bottle with sample can be heated for a while.

In case of volatile products, immediately after the filling, the density bottle clogged with its cover is wiped

with a clean, dry cloth and without fly waste or with cellulose wadding, then is introduced in the thermostat where is

maintained at 20 0.10C for 30 minutes, in order to stabilize the temperature and to allow the air bubbles to get to the

surface.If at the end of this period, the level of the liquid is modified, the density bottle is maintained in the water bath

until the level of the liquid is constant.

In case of heavy-bodied liquids, after filling the density bottle with the liquid heated and homogenized by

mixing, this is introduced (without clogging it with its cover) in a desiccation cabinet maintained at the temperature of

about 500C, in which is kept until the eventual air bubbles got to the surface of the liquid. They are broken by getting

closer a stick of glass or metal, heated, but without touching the surface of the product. The density bottle full of sample

is introduced clogged in a thermostat regulated at 20 0.1 0C where is maintained for 30 minutes. After the temperatureis constant, the density bottle is closed with its cover, which also has a temperature of 20 0.1

0C, avoiding losing the

air bubbles under it or in the length of the wall. The excess of liquid which came out from the capillary or which goes

over the marker is removed with a filter paper, until the liquid reaches the marker.

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STAS 35-81 10

After the maintain period at constant temperature passes, the density bottle is taken out from the bath avoiding

heating by the hand or by robbing it, then is taken with a paper ring and is weighted with an accuracy of 0.2 mg.

In case of necessity, the electrostatic loads are annihilated blowing over the density bottle.

In order to obtain the accurate results, the weighting is done at 200C. Although, in cases when this can not be

done, the density bottle with the sample can be weighted at another temperature in the interval 10 250C, writing

down with an accuracy of 0.10C this temperature. The far the temperature at which the weight of the product is done

from 200C, the less exact the result is.

4.4.5 CalculusThe density of the product (%

t) in g/cm

3is calculated with the formula:

(m2 m1) !ta

mDensity(!

t) = + C [g/cm

3] (3)

where:m the equivalent in water (water figure) of the density bottle at 20

0C, in g, (according to clause

4.3.2 and the note in the clause 4.3.2);

m1 the mass of the density bottle empty, weighted, in air, ing;

m2 the mass of the density bottle with sample weighted in air after correct filling at the temperature

t, ing;

!ta the density of water at temperature t, in g/cm

3, according to table 5;

C vacuum correction (of dipping into air), according to table 6 in g/cm3

.

THE DENSITY ( ! ) OF WATER AT DIFFERENT TEMPERATURES (tC) IN g/cm3

Table 5

abraded

abraded

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Table 5(cont.)

Vacuum correction (of dipping into air)Table 6

Translation NOTE: all the values in the table written with a coma(e.g.: 0,60) are to be read with a dot (e.g. 0.60)Example:

The density of a gasoline at 200C and 15

0C shall be determined. The results of the weighting are:

m = 10.3848 g;

m1= 40.6676 g;m2= 48.7688 g;

Uncorrected

density, g/cm3

Correction (C),

g/cm3

Uncorrected

density, g/cm3

Correction (C),

g/cm3

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STAS 35-81 12

The weighting was done at the temperature of 17

0C.

48.7688 40.6676

10.3848Uncorrected density = = 0.7801

From table 6 the value of the correction C = 0.00026 is obtained; the approximated value: 0.0003.

From table 5 the density of the water at 170

C = 0.99877 is obtained.Density at 17

0C = 0.7801 x 0.99877 + 0.0003 = 0.7794

Introducing this value in table 7 the density at 200C = 0.7771 is obtained.

The interpolation between the values of density (at 170C) 0.7700 and 0.7800 is used, values in which the

density of the sample are also included.

Obtaining the density at 150C is done with the table 8 where the value of 0.7771 corresponds the density at 15

0C = 0.781.

In case that the value is intermediary, the rule of simple three is used for interpolation.

4.4.6 Allowed differencesRepeatability: 0.0004 g/cm

3

Reproducibility: 0.0006 g/cm3

4.5 Determination of density of the products very heavy-bodied, semi-solid (bitumen, paraffin jelly) and solid(parafinne, ceresine parafinne, petroleum butter, ceres, etc.)

4.5.1 Equipment- density bottle according to fig. 5- thermometer up to 100 0C with the value of the division of 10C.

4.5.2 Preparation of the sampleThe sample is heated at a small flame or on water bath as much as it is necessary to flow. Superheating is

avoided.

4.5.3

Working modalityThe density bottle is filled approximately half with the sample to be analyzed, heated, pouring on a glass bar,

so as the wall of the density bottle does not get dirty at the upper part, then it is introduced unclogged in a desiccation

cabinet and is heated at 80 1000C, depending on the heavy-bodied characteristic, until the air bubbles are eliminated

(30 60 minutes). The air bubbles gathered at the surface are broken getting closer to them a heated bar without

touching the surface of the liquid. Then the density bottle unclogged, with the cover closer, is introduced in the

thermostat regulated at 20 0.10C, until the liquid takes a temperature closer to 20

0C.

NOTE In case of harder bitumen and of parafinne with low content of oil, the sample can be introduced in the densitybottle under the form of solid small pieces and then heating the density bottle with sample in the dessicatorcabinet, at a temperature with at least 10 0C higher than the soaking temperature, but of minimum 100 0C.

The cooling can also be done by maintaining the density bottle in the working chamber, provided that its

temperature is closer to 20

0

C and the air with no dust.After the cooling, the density bottle clean in exterior, dried and clogged with the cover is weighted with the

accuracy of 0.2 mg and then is filled with distilled water, cooled at 20 0.10C, is clogged with the its cover, paying

attention not to remain any air bubble on the inner surface of the wall and the cover, is dried in its exterior and it isintroduced in the thermostat in which is maintained for 30 60 minutes at the temperature of 20 0.1

0C, time in

which the level of the water in the capillary is to be to maintained constant.

The excess of water from the capillary is removed with a twisted filter paper.

After the necessary time has elapsed, the density bottle is dried, as quickly as possible, then is taken with a

paper ring and is weighted with a precision of 0.2 mg.

In case of necessity, the electrostatic loads are annihilated blowing over the density bottle.

4.5.4 CalculusThe density at 20

0C (%

20) is calculated with the formula:

(m2 m1) 0.9982

M (m3 m2)Density (%

20) = + C [g/cm

3] (4)

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STAS 35-8113

in which:

m the equivalent in water (water figure) of the density bottle at 200C, ing, (according to clasuse

4.3.2);

m1 the mass of the density bottle empty, ing;

m2 the mass of the density bottle partially filled with sample, at 200C, ing;

m3 the mass of the density bottle with sample and distilled water at 200C, ing;

C correction of the vacuum (of dipping into air) in g/cm

3

, according to table 6;0.9982 density of water at 20

0C according to table 5, in g/cm

3.

Example:

The density of a crude parafinne at 200C shall to be calculated.

The results of the weights are:

m= 24.8512 g;

m1= 38.8116 g;

m2= 41.5882 g;

m3= 63.3310 g;

41.5882 38.8116

24.8513 (63.3310 41.5882)Uncorrected density = = 0.8932 [g/cm

3]

From table 6 based on the value of uncorrected density is obtained:

C = 0.0001

%20

= 0.8932 x 0.9982 + 0.0001 = 0.8917 [g/cm3]

4.5.5 Allowed differencesAccording to clause 4.4.6

5. CALCULATION OF RELATIVE DENSITY

5.1.The relative density of the liquid product at t 0C compared to water at the same temperature, is calculated with theformula:

pt

pta

Relative density (dtt) = (5)

where:

pt density of the sample at t

0C, in g/cm

3;

pta density of the water at t

0C (according to table 5) in g/cm

3.

Most frequently in Romania is required that the relative density at 200C compared to water at 20

0C (d

20

20 or

the relative density at 150C compared to water at 15

0C (d1515 ).

In these cases the relative density of the product is calculated as follows:

9991.0,

9982.0

1515

15

2020

20

!!"" dandd

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STAS 35-81 14

DENSITY CORRECTED AT 200C

From 0.500 to 0.590 g/cm3 25

0C 0

0C

Table 7

Translation NOTE: all the values in the table written with a coma(e.g.: -25,00) are to be read with a dot (e.g. -25.0)

The temperature of

the determination,0 0C

Value read on the areometer

Densit corrected at 200C /cm

3

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STAS 35-8115


From 0.500 to 0.590 g/cm3to 0

0C 25

0C

Table 7(cont.)


The temperature ofthe determination

, 00

C



3

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STAS 35-81 16


From 0.500 to 0.590 g/cm3to 25

0C 50

0C

Table 7(cont.)


The temperature of

the determination,

0 0C



3

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STAS 35-8117


From 0.600 to 0.690 g/cm3to -25

0C 0

0C

Table 7(cont.)


The temperature of

the determination,

0 0C



3

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STAS 35-81 18


From 0.600 to 0.690 g/cm3to 0

0C 25

0C

Table 7(cont.)


The temperature of

the determination,

0 0C



3

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STAS 35-8119

DENSITY CORRECTED AT 20

0C

From 0.600 to 0.690 g/cm3to 25

0C 50

0C

Table 7(cont.)


The temperature of

the determination, 00C


Densit corrected at 200

C /cm3

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STAS 35-81 20


From 0.700 to 0.790 g/cm3to -25

0C 0

0C

Table 7(cont.)


The temperature of




3

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STAS 35-8121


0C

From 0.700 to 0.790 g/cm3to 0

0C 25

0C

Table 7(cont.)


The temperature of



Densit corrected at 20 0C /cm3

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STAS 35-81 22


From 0.700 to 0.790 g/cm3to 25

0C 50

0C

Table 7(cont.)


The temperature ofthe determination,

0 0C



3

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STAS 35-8123


0C

From 0.700 to 0.790 g/cm3to 50

0C 75

0C

Table 7(cont.)


The temperature of

the determination,

0 0C



C /cm3

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STAS 35-81 24


From 0.800 to 0.890 g/cm3to -25

0C 0

0C

Table 7(cont.)


The temperature of

the determination,

0 0C



3

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STAS 35-8125


0C

From 0.800 to 0.890 g/cm3to 0

0C 25

0C

Table 7(cont.)


The temperature of

the determination,

0 0C



C /cm3

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STAS 35-81 26


From 0.800 to 0.890 g/cm3to 25

0C 50

0C

Table 7(cont.)


The temperature of

the determination,0 0C



3

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STAS 35-8127


0C

From 0.800 to 0.890 g/cm3to 50

0C 75

0C

Table 7(cont.)


The temperature of

the determination,

0 0C



C /cm3

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STAS 35-81 28


0C

From 0.800 to 0.890 g/cm3to 75

0C 100

0C

Table 7(cont.)


The temperature of

the determination,

0 0C



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STAS 35-8129


From 0.900 to 0.990 g/cm3to -25

0C 0

0C

Table 7(cont.)


The temperature of

the determination,

0 0C



3

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STAS 35-81 30


From 0.900 to 0.990 g/cm3to 0

0C 25

0C

Table 7(cont.)


The temperature of

the determination0 0C



3

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STAS 35-8131


0C

From 0.900 to 0.990 g/cm3to 25

0C 50

0C

Table 7(cont.)


The temperature of

the determination,

0 0C



C /cm3

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STAS 35-81 32


From 0.900 to 0.990 g/cm3to 50

0C 75

0C

Table 7(cont.)


The temperature of

the determination,

0 0C



3

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STAS 35-8133


From 0.900 to 0.990 g/cm3to 75

0C 100

0C

Table 7(cont.)


The temperature of

the determination,

0 0C



3

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STAS 35-81 34


0C

From 0.900 to 0.990 g/cm3to 100

0C 125

0C

Table 7(cont.)


The temperature of

the determination,

0 0C



0

C /cm

3

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STAS 35-8135


From 1000 to 1090 g/cm3to 0

0C 25

0C

Table 7(cont.)


The temperature of

the determination,

0 0C



3

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STAS 35-81 36


0C

From 1000 to 1090 g/cm3to 25

0C 50

0C

Table 7(cont.)


The temperature of

the determination,

0 0C



0

C /cm

3

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STAS 35-8137


From 1000 to 1090 g/cm3to 50

0C 75

0C

Table 7(cont.)


The temperature ofthe determination,

0 0C



3

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STAS 35-81 38


From 1000 to 1090 g/cm3to 75

0C 100

0C

Table 7(cont.)


The temperature of

the determination,

0 0C



3

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STAS 35-8139


0C

From 1000 to 1090 g/cm3to 100

0C 125

0C

Table 7(cont.)


The temperature of

the determination,

0 0C



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STAS 35-81 40

TRANSFORMATION OF DENSITY AT 200C (g/cm

3) IN DENSITY AT 15

0C (g/cm

3)

Table 8

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STAS 35-8141

Table 8 (cont.)

Translation NOTE: all the values in the tables above written with a coma (e.g.: 0,620) are to be read with a dot (e.g.

0.620)

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STAS 35-81 42

6. MENTIONS IN THE ANALYSIS BULLETIN

The following are mentioned in the analysis bulletin:

- data for identification of the product which is being analyzed;- the method used;- the result obtained;- STAS 35-81.

__________________

Elaborated by THE MINISTER OF CHEMICAL

INDUSTRY

- Institute of research, technology engineering anddesign of refinery Ploiesti

Responsible for the project: Eng. Mihai Conrad

Final drafting: STANDARDIZATION ROMANIANASSOCIATIONService of Mining, Petroleum, and Light Industry and

Agricultural-Food Industry

Eng. Doina Sandu

Collaborators:- Industrial Power Plant of Refinery and Petroleum

Chemistry Ploiesti

- Power Plant of Commercializing the Petroleum ProductsPECO Bucharest

-

Metrology National Institute- Petroleum Products Integrated oil-well Work Borzesti- General Direction of State Reserves- Transportation Enterprise and Commercializing of

Petroleum Products Ploiesti

Documents

STAS 35-81 R