Westphal balance

Saturated solutions of DDT in the various solvents were prepared by heating and storing at three lower temperatures for at least 48 hours after crystal formation. Samples of the supernatant solutions at the test temperatures were taken and their densities were determined at room temperature 75 to 77 F. If the amount of supernatant liquid was sufficient a Westphal balance was used for smaller amounts, the density was calculated from the weight of a pipetted volume. 

In addition to lactometry (determination of the extent to which a hydrometer sinks), the density of milk can be measured by pycnometry (determination of the mass of a given volume of milk), by hydrostatic weighing of an immersed bulb (e.g. Westphal balance), by dialatometry (measurement of the volume of a known mass of milk) or by measuring the distance that a drop of milk falls through a density gradient column. 

Various types of balances may be employed with this method, such as ordinary analytical balance, chainomatic balance and Westphal balance. The most rapid of these is the Westpkal Balance or its modifications. Its accuracv is... 

Analytical Methods of Powder Analysis , Bofors, Sweden (I960), 22 (Mohr-Westphal Balance Method), 22-23 (Pycnometer Method), 23 (Bulk Density), 172 (Modified Bianchi Method for detg sp gr of smokeless proplnts), and 173 (Bulk Density detn of smokeless proplnts)... 

Specific Gravity,—This can be determined in the usual way, with the Westphal balance, the picnometer, or the densimeter, at 150. The following procedure is the most common and is carried out on the milk as it stands or on the whey. 

Specific Gravity.—This is measured by means of a hydrometer or, more accurately, by a picnometer. The viscosity renders it difficult to use a Westphal balance. 

The specific gravity of a beer, also termed " present gravity " or attenuation gravity, is determined on the gas-free beer at 15 5° C. (6o° F.)—with reference to water at the same temperature—by means of a specific gravity bottle or a Westphal balance (see Spirits). 

This is measured at 150 C., with respect to water at the same temperature, by means of a tested Westphal balance (see Spirituous Liquors) sensitive to the fourth decimal figure. 

Specific Gravity.—This is determined at 150 by means of the Westphal balance (see chapter on Spirits). 

Apparatus and Methods of using them. Use is generally made of the Westphal balance or the picnometer. 

Westphal balances are sometimes graduated at other normal temperatures, e.g., 17-5° or 20 according to the purposes for which they are intended. 

Before making use of the alcoholic liquid thus diluted, it is always advisable to verify, by means of the Westphal balance, the specific gravity, which should be exactly 0-9656 at 150 C. 

This is measured in the usual way, i.e.,with a Westphal balance or picnometer, generally at 150 C. If only a small quantity of material is available, use may be made of a small U-shaped picnometer (see Spirits, p. 233). If a temperature other than 150 is used, the result may be corrected by means of the coefficient o 00075, to be added for each degree above, or subtracted for each degree below, 150 C. 

Specific Gravity.—The sp. gr. of tanning solutions is determined (usually at 150 C.) with the Westphal balance or with a hydrometer or, in industrial practice, with the Baume hydrometer.2... 

A large volume expansion for solutions of sodium in ammonia was first reported by Kraus and Lucasse (17). Since this initial report, many investigations have been made of the volume expansion for a number of alkali metal-ammonia solutions. The techniques employed in these investigations have varied from density measurements for concentrated solutions using the Westphal Balance or Pycnometer to dilatometric studies for dilute solutions, which measure the volume expansion directly. 

Analysis gave 76.68 and 76.85 per cent bromine, the theory being 76.88 per cent bromine. The yield is almost quantitative. The specific gravity by the Westphal balance method is 2.688 at 20°C. It freezes at — 52°C. Thionyl bromide decomposes slowly on standing and should be kept in bottles with tight-fitting glass stoppers. 

In AOCS Official Method Cc 10b-25 (Firestone, 1998) for determining the specific gravity of solid fats at 25°C, the specific gravity of an ethanol-water mixture, in which a small solid sample of the fat neither sinks nor floats, is measured using a Westphal balance (which utilizes the Archimedes buoyancy principle). The specific gravity of the fat sample is equal to this measured value. 

Westphal Balance Method (Alternative Method). Sp gr shall be detd in accordance with Federal Test Method No 141 Method 4183, except that the temp shall be 20/20 °C... 

Note Westphal Balance Method is described under Hydrostatic Weighing Method in Vol 3 of Encycl, p D68... 

If time permits, the densities of the solutions should be measured with a Westphal balance. Otherwise, the densities may be taken equal to that of the pure solvent without introducing appreciable error. 

Glass-walled thermostat bath at 25°C or substitute polyvinyl alcohol (M —60,000 to 80,000) 5 g of solid or 200 mL of solution containing 18 g L KIO4 (1 g) chromic acid or other cleaning solution (50 mL) Westphal balance, if needed. The polyvinyl alcohol can be obtained from Polysciences Inc., 400 Valley Road, Warrington, PA 18976, and many other suppliers. 

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