_Fixed Acid._--The quantity of fixed acid, consisting principally of oleic and stearic, in pure lard should not be less than 93 percent. The total quantity of free acid in lard, that is, acid uncombined with the glycerine, should not exceed one-half of one percent, and in neutral lard should be much less than this. _Quantity of Iodin Absorbed._--All common fats and oils have the property of absorbing, under given conditions, certain quantities of iodin. Lard of the highest quality should not absorb more than 60 percent of its weight of iodin. The lard made from the feet and certain other parts of the animal, however, may have a larger iodin number, rising as high as 75 or even 80. =Properties of Lard.=--The average properties of different classes of lard in relation to physical and optical conditions are shown in the following table: RE- RISE OF TEMPER- SPECIFIC MELTING FRACTIVE ATURE WITH IODIN GRAVITY. POINT. INDEX. SULFURIC ACID. WATER. ABSORBED. 35° C. ° C. 25° C. ° C. PERCENT. PERCENT. .9053 40.7 1.4620 41.5 .077 62.48 The above table is the average composition of nineteen samples of lard furnished under affidavits of purity and which appear from their chemical and physical properties to be composed purely of the fat of swine taken from those parts of the animal usually devoted to lard making. The average data may be regarded as representing the properties of the ordinary pure commercial lard on the market. =Average Properties of Steam Lard.=--Below is given the average composition of eleven samples of steam lard furnished under affidavit and, apparently, as judged by their chemical and physical properties, composed solely of the fat of swine. Steam lards are not of as high a quality as the lards contained in the preceding table. They have usually a distinctively strong odor, quite different from that of lards which are rendered in open kettles at low temperature and from selected portions of fat. RE- RISE OF TEMPER- SPECIFIC MELTING FRACTIVE ATURE WITH IODIN GRAVITY. POINT. INDEX. SULFURIC ACID. WATER. ABSORBED. 35° C. ° C. 25° C. ° C. PERCENT. PERCENT. .9055 37.0 1.4623 39.9 .109 62.86 =Properties of Adulterated Lards.=--It is possible to mix together the different materials used in making adulterated lard in such a manner as to produce a compound which in some respects resembles the natural product. This compound, however, necessarily differs from the natural product in its physical and microscopic properties and in its reaction with various chemicals which give distinct color with the different fats and oils used as adulterants. The mean properties of thirteen samples of mixed or compound lards are shown in the following table: