Pyknometer

If the solute is a liquid, introduce it into the apparatus from an ordinary pyknometer tube (Fig. 80), weighing the tube before and after. For this purpose, insert the delivery-tube of the pyknometer carefully down the side-arm A (Fig. 79) so that the liquid falls well into the body of T. Force the liquid... 

ITi = weight in air of the water required to fill the pyknometer at fC W2 = weight in air of the liquid required to fill the pyknometer at t°C d = density of water in grams per milliliter at fC Sync = specific gravity of the liquid at t°C referred to water at t°C corrected for the buoyant effect of air... 

Density (actual) Design of treatment/disposal/ Pyknometer... 

Determination of Specific Gravity.—A simple method for determining the specific gravity of liquids is as follows I. pyknometer, or small glass bottle, is used of about 20 to 30 c.c. capacity, with narrow neck, upon which a mark is etched and which is closed by a ground glass stopper (Fig. 45). 

A very delicate and useful piece of apparatus, which is leadily made with the blow-pipe, is Perkins modification of Sprengel s pyknometer. It is especially adapted for small quantities of liquid and for the moie volatile ones. The apparatus (Fig. 46) consists of a U l ube to hold from 2 to 10 c.c., drawm out at each end into a fine capillary. The one capillaiy limb, a, is bent outwards and is furnished with a small bulb the other, b, is bent at a right angle with the first. On the limb a, between the bulb and the top of the U-tnbe a mark is etched. The... 

The densities of polymers can be determined by the pyknometer technique or by the flotation method. In the pyknometer technique the liquid volume displaced by the polymer sample is determined by weighing. Most polymers have a density larger than that of water, which can, therefore, be used as the liquid. Polymers in the form of powders or pressed discs tend to adsorb or occlude air bubbles, which can lead to serious errors. This can be largely prevented by careful degassing of the pyknometer and polymer sample under vacuum before filling with liquid, and/or by addition of a small amount (0.1%) of commercial detergent to lower the surface tension of the water. 

The density of the liquid mixture can be determined using a pyknometer or it can be derived from a previously determined calibration curve. For the determination of densities less than unity (e.g., polyethylene), ethanol/water mixtures are suitable for densities larger than unity one may use mixtures of water with aqueous salt solutions (40% CaCl2 solution = 1.40 g/ml 72% ZnCl2 solution = 1.95 g/ml). The density gradient method, which is an elegant var-... 

Apparatus used to measure solid volumes are often referred to as pyknometers or pycnometers after the Greek pyknos meaning thickness or density. Once the sample volume and mass have been determined, the density is readily calculated. 

ISO 1183-1 2004. Methods for determining the density of non-cellular plastics - Part 1 Immersion method, liquid pyknometer method and titration method. 

The density of a liquid is most easily determined by means of vessels known as pyknometers, the volume of which need not exceed 1 c.c. Perkin s modification (Fig. 42) of the Sprengel pyknometer is well adapted for small quantities of liquid and also for volatile liquids. The apparatus which usually has a volume of 2—10 c.cs. consists of a U-tube, the limbs of which are drawn out to capillaries, and bent as shown. On limb A a small bulb is blown, and below this a ring is etched round the capillary. 

Im Diagramm 31 sind die mit dem Pyknometer gemessenen Dichten der bei Zimmertemperatur fliissigen Glieder homologer Reihen mit ver-schiedener Basisgruppe gezeichnet. 

Density is determined by pyknometry at a standard temperature of 25°C. For standards, see Table 1.1 ( Density ). Apparatus pyknometer, vacuum pump or centrifuge. 

Quoted density values in standard reference works are of the materials true density. If density is determined using a gas pyknometer, the volume measured would include closed pores but exclude open pores i.e. the measured density would be the apparent density. If the suspending liquid penetrates all the cracks and fissures on the particle surface, the measured volume would be the same as that determined by gas pyknometry but the total mass would be greater due to the included liquid that will remain with the particle as it falls in the liquid, hence its sedimentation density will be intermediate between the apparent density and the true density and greater than the effective density. These differences are usually not highly significant for coarse particles unless they are highly porous. 

In density determination the volume of fluid, displaced by a known weight of powder, is determined. Since weight can be measured accurately, the problem is that of accurate determination of volume. With pyknometers (or density bottles) the fluid is a liquid, usually water with surfactant, unless the powder is water miscible. With gas pyknometers the fluid is usually dry air or helium. 

May and Marienko [120] used a 1 cm micropyknometer, with ethylene glycol as the fill liquid, for measuring the density of small amounts of material. Stein et. al. [121] found this method time consuming and difficult and developed a method in that air was used as the fill liquid. Their micropyknometer had a 2 mm bore stem, accurately calibrated with mercury, at 0.30 cm and 0.50 cm. A known weight of powder was placed in the pyknometer and the neck sealed with a mercury plug. This was forced down to the 0.50 cm level in a pressure chamber at pressure Pj and then to the 0.30 cm level at pressure P2. The volume of powder (F) is given by ... 

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