With oils the use of the Halphen and Bechi tests will be found to be useful as a means of approximately determining the amounts of adulteration present. If Halphen gives a reaction and Bechi does not, the adulteration with cottonseed oil is probably less than 10 percent.
The admixture of beef fat with lard is best detected by means of the microscope. The fat is dissolved in ether and allowed to slowly crystallize. If it is composed of pure lard the crystal assumes a form which is represented in [Fig. 8].
If, on the other hand, beef fat be mixed with lard, the crystals will assume a radiated fan-shaped appearance shown in [Fig. 9]. Even one who is an expert with the microscope may not be able without some difficulty to detect these adulterations by the simple tests above mentioned.
Fig. 8.—Lard Crystals. × 140.—(Bureau of Chemistry.)
Fig. 9.—Beef Fat Crystals. × 140.—(Bureau of Chemistry.)
Commercial Classification of Lards.
—In addition to the kinds of lard mentioned above other varieties are known in commerce.