Density weighing bottle

There are other methods for the determination of density. These include the specific gravity balance and the use of a pycnometer (weighing bottle). 

Accuracy density data were obtained with high temperature dilatometers, where the solution is contained in a stainless-steel autoclave connected through a capillary tube to a mercury reservoir thermostatized at 25 °C. When the sample autoclave is heated, the solution expands and the excess mercury is discharged into a weighing bottle, to keep the pressure constant. 

It is rarely that any greater degree of accuracy than that attained in the above methods is required. If, however, scientific accuracy is necessary in specific gravity determinations, the usual standard of comparison, at whatever temperature the determination may be made, is water at its maximum density temperature, namely 4°. If no correction is made for the weight of the air contained in the bottle or tube, accuracy to the fourth place of decimals is ensured by reducing the observed weighings to vacuum weighings. This can be done by the equation—... 

Procedure. Weigh 20 g of air-dry soil sieved to 2 mm into a 250-ml wide-mouth high-density polyethylene screw-cap bottle. The square type bottles fit best the square box of the reciprocating shaker. Add 100 ml 1 M KCI and shake for 15 min. Transfer all the suspension to a filter funnel holding a Whatman No. 6 paper, and collect the filtrate. When leaching has ceased, add two successive 50-ml aliquots of 1 M KCI. Combine the leachates from the total addition of 200 ml (some will be retained in the soil) and mix. 

A preliminary step necessary to precise work with the pycnometer is the determination of its two volume constants that is, the constants of the linear equation expressing die capacity as a function of die temperature. This is done by filling with distilled water and weighing accurately several times at each of two temperatures near the ends of the range for which the pycnometer is to be used. The bottle form is also adapted to the precise measurement of densities of solids. See also Specific Gravity. 

Specific gravity is the density (mass per volume) of the sample compared to the density of water (see Table Gl.5.7 in Anticipated Results). Samples are equilibrated to the same temperature and weighed using a pycnometer. The pycnometer is a sample bottle that provides a constant volume. 

Density per se is measured by weighing the sample in a volume-calibrated pycnometer or density bottle using, for example, the IUPAC standard method 2.101 (Paquot and Hautfenne, 1987). 

A bottle weighed 7.6500 g empty and 9.9700 g after introduction of an organic liquid with a density of 0.92 g/cm. The balance was equipped with stainless steel masses d = 8.0 g/cm- ). Correct the mass of the sample for the effects of buoyancy. 

The density of the specimen, as determined by weighing a quantity of the powder in a pyknometer bottle, was 5.82 gm/cm. We then find, fVom Eq. (3-7), that... 

Directions Set up the apparatus represented in Fig. 8. A test tube, A, placed in cold water in a gas bottle serves to collect the distillate. (1) Weigh a graduated cylinder to decigrams. Place in the graduate 15 c.c. of methyl alcohol, note the volume to 0.1 c.c. and weigh again. (2) Calculate the density of the alcohol. Pour the alcohol into the flask. Wash out the cylinder with water and then add 30 c.c. of water to the alcohol. Shake the mixture so that it is uniform. Dry the cylinder. Pour into it the mixture. Note the volume accurately and weigh. (3) Calculate the density of the mixture. 

ISO 2781 also details a procedure (method B) for use when it is necessary to cut the sample into small pieces to avoid trapped air. as might happen with narrow bore tubing. The test piece comprises a number of small smooth pieces within the size 4mm X 4mm x 6mm. These are weighed in a density bottle both with and without the remaining space filled with water. The bottle is also weighed without rubber both empty and filled with water. This is a more tedious procedure than method A and is generally only used as a last resort. Even with the test piece cut up, trapped air can still be a problem. 

For coarser powders, i.e., particle size >10 pm, a liquid pycnometer is used. A calibrated bottle is weighed, with mass mo, and the powder is added, with total mass mj. A liquid with density, di, is then added, with total mass m2. It the pycnometer bottle contains only the liquid, i.e., no powder, has a mass m3, the apparent density of the particles is given by ... 

If Alfred inspects the bottles carefully, he should be able to see whether the contents are solid (silver) or liquid (mer-cuiy). Alternatively, since mercury is more dense than silver, the bottle of mercury should weigh more than the bottle of silver (the question indicated that both bottles were of similar size and both were full). Density is mass/volume. 

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