Butyrometer

BUTYROMETER (from Latin butyrum—butter and Greek metron—measure), an instrument for determining the amount of fat in milk. Among various designs of butyrometers, only the Gerber butyrometer and, to some extent, Marchand's lactobutyrometer have gained the greatest practical application.—The Gerber butyrometer (see Figure 1, R. B.) is a small cylindrical glass vessel, the upper part of which is drawn out into a long neck ending in a small bulb, while the lower part has an opening closed with a rubber stopper. A series of fine graduations is marked on the neck for reading the amount of fat separated from the milk. Among the modifications of the standard butyrometer, the flat butyrometer (see Figure 1, F. B.) deserves attention, as its neck is more convenient for reading the fine scale graduations. For analyzing skimmed milk, butyrometers are manufactured with a relatively large cylindrical

FIG. 1.

body and a short neck (see Figure 1, S. B.). Gerber butyrometers are also used to determine the amount of fat in various dairy products. When examining cream and sour cream, two types of butyrometers are used: in one, 5 g of cream or sour cream is poured directly; in the other (see Figure 2), weighing is performed in a special cup, which is then inserted inside the butyrometer together with the stopper. Butyrometers for butter have a similar device (with a cup). (The procedure for using the butyrometer is described in detail in the article Acid-butyrometry.) In addition to the usual acid method for determining fat in a butyrometer, the Gerber-Wendler method ("Sal") is also very widespread; it consists in pouring 11 cm³ of a special "Sal" solution, 0.6 cm³ of isobutyl alcohol, and 10 cm³ of the milk under test into the butyrometer, plugging the butyrometer with a rubber stopper, and vigorously

shaking it until the milk proteins are completely dissolved; then the butyrometer is placed for 5–10 minutes in a water bath at 45°, after which it is centrifuged in the usual manner and the amount of separated fat is read. The accuracy of the "Sal" method is identical to the acidimetric method. The "Sal" solution is prepared from 150 g of caustic soda, 40 g of Rochelle salt, and 10 g of sodium chloride in 1 L of water. There are two other methods for determining fat using Gerber butyrometers: Sichler's method ("Sinacidbutyrometry") and Wendler's method ("Neosal"). Both of these methods are rarely used and offer no special advantages over the described basic methods.—For a description of Marchand's butyrometer, see Lactobutyrometer.