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. [Illustration: FIG. 8.--LARD CRYSTALS. × 140.--(_Bureau of Chemistry._)] [Illustration: 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. =Neutral Lard.=--This, which is one of the best varieties of lard, is made from the fat derived from the leaf lard of the slaughtered animal in a perfectly fresh state, that is, taken immediately after slaughter and before the carcass is cold. The leaf lard, when it is removed from the animal, is at once placed in cold storage or put into cold water, in order to rapidly remove the animal heat. As soon as it is thoroughly chilled it is reduced to a pulp in a grinder and sent at once to the rendering kettle. The fat is rendered at a very low temperature, from 105 to 120 degrees F. (40-50 degrees C). It is evident that only a part of the lard is separated at this temperature, and this part is regarded as being of the best quality, almost tasteless, free of acids and other impurities. The residue from the making of neutral lard is sent to other kettles, where it is subjected to a higher temperature and the remainder of the lard extracted, which is sold under the name of another grade. Neutral lard, obtained as above, while still liquid, is washed with water containing a trace of sodium carbonate, common salt, or a dilute acid. The product thus formed is almost neutral in its reaction to litmus paper containing not to exceed .25 percent of free acid, but it has more water and mineral matter than is found in the pure rendered untreated lard. The neutral lard made in this way is not used so commonly for culinary purposes but chiefly in the manufacture of oleomargarine. =Leaf Lard.=--The residue of lard obtained by rendering the unseparated part of lard from the above process at a higher temperature is also of a high quality and is sometimes improperly designated leaf lard, a term which should be reserved for the whole product instead of a part obtained by rendering the residual leaf fat.