THE INVESTIGATION AND TESTING OF BUTTER. 197 



with certainty from animal-fat. The discovery of the Hehner method 

 rendered this possible. In this method, the fat to be tested, after being 

 prepared in a pure solution, is saponified, the soap thus obtained is decom- 

 posed, the soluble and insoluble acids separated, and the total weight of 

 the palmitic, stearic, and oleic acids estimated. The sum of these three 

 insoluble fatty acids varies in pure butter-fat from 85*5 to 89*8 per cent, 

 and rarely exceeds in all the rest of the fats 95 -5 of the total fat investi- 

 gated. A simple and much-used method, based upon a similar principle 

 as the Hehner, is the Reichert. It was first somewhat changed by 

 Meiszl and subsequently perfected by Woolny. The Koettstorfer 

 method has also proved itself very useful. This method recommends 

 the determination of the capacity for saturation of the acids in the 

 fat investigated, by the number of milligrammes of potassium hydrate 

 required for saponifying 1 gram of fat. This saturation equivalent varies 

 for pure butter-fat, according to the experiments that have been performed 

 so far, between 221 and 233 '4 milligrammes of potassium hydrate. The 

 other fats and oils show a lower saturation equivalent, generally from 197 

 to 178 milligrammes of potassium hydrate. 



If butter has to be tested for the detection of foreign fats, a definite 

 opinion may be formed by determining, first, the sum of the insoluble 

 fatty acids by the Hehner method; secondly, the relative percentage of 

 volatile fatty acids by the Reichert-Meiszl-Woolny method ; thirdly, the 

 refraction coefficient at 22 C. ; fourthly, the specific gravity of the fat 

 at the boiling temperature of water; and fifthly, perhaps also by the 

 Koettstorfer method. The number of c.c. of a tenth normal alkaline 

 solution required for 5 grams of butter-fat in carrying out the Reichert- 

 Meiszl- Woolny method varies, in most cases, between 21 and 33, and 

 the specific gravity of pure butter-fat lies between -8650 and '8685 at 

 100 C. The determination of the so-called iodine coefficient is, owing 

 to the great variation which it may exhibit, not well suited for the detec- 

 tion of foreign fats in butter. The complete analysis of butter can be 

 carried out as follows : 



(1) Determination of Water. 5 to 10 grams of butter are weighed in 

 a small glass capsule, lightly covered, and are then allowed to melt on 

 the air-bath. The melted fat, after it has become clarified, is filtered in 

 the air-bath on to a weighed filter into a little weighed capsule, care being 

 observed in pouring it out that all the fat and nothing of the watery mass 

 lying beneath the fat is poured on to the filter. The watery residue in the 

 glass beaker is then dried at 100 C., and is left along with the fat in the 

 capsule and on the filter, which should remain, if possible, standing in a 

 dry shelf, cooled in the desiccator, and weighed. This is repeated until 

 the weight obtained by two subsequent weighings shows at most a milli- 



