Specific Gravity of Fallout Dust Pycnometer Method

Determination of Specific Gravity of Fallout dust Pycnometer method with reference to ASTM D854-2.


Specific gravity (Gs) of a solid substance is the ratio of the weight of a given volume of material to the weight of an equal volume of water. In effect, it tells us how much heavier (or lighter) the material is than water. For exact analysis, the specifications require distilled or de-mineralized water.  Soil’s specific gravity largely depends on the density of the minerals making up the individual soil particles.  Two specific gravity readings were obtained from the one sample and the average has been used to provide the specific gravity of the sample.


2.1 Apparatus Used for Determining Specific Gravity:

Pycnometer (10millimetre capacity), Mortar and pestle, laboratory Oven, Heat resistant gloves, Stirring spatula, Distilled water, Desiccator, Thermometer. Balance scale sensitive to 0.01 gram

2.2 Sample Preparation.

Fallout dust was oven dried using a laboratory oven for 6 hours. Fallout dust was placed on a desiccator for 60 minutes to cool. Desiccator was used to prevent loss and dilution of fallout dust material. Cooled dried sample materials were broken down using mortar and pestle.

2.3 Determination of Specific Gravity

Specific gravity of the fallout dust was determined in the laboratory using a pycnometer method with reference to ASTM D854-2 using de-ionized water at 20 ⁰C. A 10 ml pycnometer was filled with water to the meniscus and the mass of the pycnometer filled with deionised water was determined denoted by the variable Ma.  Exactly
3.4 ml of water was withdrawn from the pycnometer to make space for the dust, the pycnometer was left with 6.6 ml of water and about 2 g (Mo) of dust was added to the 6.6 ml water in the pycnometer. The pycnometer was closed with 6.6 ml of deionized water and about 2 g of dust was gently rolled on a smooth table for about 10 minutes to remove air bubbles.  Water in the pycnometer was filled to meniscus again while making sure that no dust materials were stuck on the neck of the pycnometer.  Mass of the pycnometer that was filled with water and fallout dust sample (Mb) was recorded after 12 hours of curing.  Specific gravity of the dust samples was computed using the following formula.

Gs = ___Mo.K_______
Mo + (Ma – Mb)

Where:       Gs = Specific Gravity

Mo = Mass of Oven Dried fallout dust Materials (g)

K   = Temperature correction factor (of which at 20 ⁰C =1)

Ma = Mass of the pycnometer filled with De-ionized water (g)

Mb = Mass of the pycnometer filled with water and fallout dust sample (g)


Figure 1: apparatus used for determining specific gravity; (A) laboratory oven for drying the fallout dust, (B) Desiccator for cooling the samples, (C) Mortar and pestle for breaking down the dust sample lumps with pycnometers, (D) Mili-Q de-ionised water generator, (E) Scale balance for determining the weight.



The results were recorded in a spreadsheet and summarised (Table 1)

Table 1: Specific Gravity of the Samples (Generic Results)

Sample I.D Mo( g) Ma(g) Mb(g) Gs
1SPA 2.00 22.34 23.59 2.67
2SPB 2.00 22.34 23.60 2.70
Average Gs 2.69


Specific gravity of the dust samples was determined as shown in Table 1.  Specific gravity of the dust sample was found to be 2.72 times that of water.  The fallout dust materials were denser than water.  Since the Specific gravity was determined at 20 ⁰C, the temperature did not have effect on the determined Specific gravity since its correction factor (K) is equal to 1 as supported by the table below:












Pycnometers filled with de-ionised water and fallout dust materials

Lutendo (DustWatch geology consultant) crushing dust using pebble and mortar

Specific Gravity of Fallout Dust Pycnometer Method

Gerry F. Kuhn (FMVS, MSAIOH, Grad SE) Chris Loans
(BSc Chemical Engineer, Pr Eng)
Cape Town, Doc Number:  0617291001  Date:  29-Jun-17


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