38 PROVISIONAL METHODS FOR ANALYSIS OF FOODS. 



finally sprayed into ice-cold water so as to give the product that granular appearance 

 usually found in butter just from the churn. It is then treated and sold as butter. 

 When this product, or its mixture with butter, is sold as butter it should be consid- 

 ered an adulteration. In addition to the special methods given below for the detec- 

 tion of process butter, the general methods described under Edible Fats and Oils 

 must often be employed. Excessive amounts of water or of casein should be regarded 

 as adulterations. Occasionally preservatives other than salt are added to butter, but 

 they are generally the same as those found in milk. 



2. DETERMINATION OF WATER.* 



Place from 1.5 to 2.5 grams of the sample in a flat-bottomed dish having a surface 

 of at least 20 square centimeters, and dry to constant weight at the temperature of 

 boiling water. 



The use of clean, dry sand or asbestos with the butter is admissible, and is neces- 

 sary if a dish with round bottom be employed. 



3. DETERMINATION OF FAT. a 



(a) DIRECT METHOD. 



Dry the butter on asbestos or sand to determine the water, and extract the fat 

 by anhydrous alcohol-free ether. Evaporate the ether from the extract, heat to 

 constant weight at the temperature of boiling water, and weigh. 



(b) INDIRECT METHOD. 



Dissolve the dry butter from the water determination in the same dish with 

 absolute ether or with 76 C. petroleum ether. Then transfer the contents of the dish 

 to a weighed Gooch crucible with the aid of a wash bottle filled with the solvent, 

 and wash until free from fat. Heat the crucible and contents at the temperature of 

 boiling water until the weight is constant, and calculate the weight of fat from the 

 data obtained. 



4. DETERMINATION OF REICHERT-MEISSL NUMBER. 



Employ the official method of the association. b 



5. DETERMINATION OF SAPONIFICATION VALUE. 

 Proceed as directed on page 26. 



6. THE WATERHOUSE TEST FOR OLEOMARGARINE. c 



Half fill a 100-cc beaker with sweet milk, heat nearly to boiling, and add 5 to 10 

 grams of butter or oleomargarine. Stir with a small rod, preferably of wood and 

 about the size of a match, until the fat is melted. Then place the beaker in cold 

 water and stir the. milk until the temperature falls sufficiently for the fat to congeal. 

 At this point the fat, if oleo, can easily be collected into one lump by means of the 

 rod, while if butter it will granulate and can not be so collected. The distinction is 

 very marked. 



7. SPECIAL TESTS FOR PROCESS BUTTER. d 



(a) FOAM TEST. e 



Heat 2 or 3 grams of the sample, either in a spoon or dish, over a free flame. 

 True butter will foam abundantly, whereas process butter will bump and sputter, 



U. S. Dept. of Agr., Div. of Chem., Bui. 46 revised, p. 43. 



b U. S. Dept. of Agr., Div. of Chem., Bui. 46 revised, pp. 44-46. 



c Jour. Am. Chem. Soc., 1901, 23, 200; U. S. Dept. Agr., Farmers' Bui. 131, p. 7. 



d See Appendix, p. 152. 



Jour. Amer. Chem. Soc., 1900, 22, 150; U. S. Dept. of Agr., Farmers' Bui. No. 131. 



