294 METHODS OF ANALYSIS [Chap. 



BUTTER AND ITS SUBSTITUTES. 



39 PREPARATION OF SAMPLE.-OFFICIAL. 



If large quantities of butter are to be sampled, use a butter trier or sampler. 

 Melt completely the portions thus drawn, 100-500 grams, in a closed vessel at as 

 low a temperature as possible. When softened, cool and, at the same time, shake 

 the mass violently until it is homogeneous and solidified sufficiently to prevent the 

 separation of the water and fat. Then pour a portion into the vessel from which 

 it is to be weighed. The sample should completely or nearly fill the vessel and 

 should be kept in a cool place until analyzed. 



40 MOISTURE.— OFFICIAL. 



Weigh 1.5-2.5 grams of the sample into a flat-bottomed dish, having a surface 

 of at least 20 sq. cm., dry at the temperature of boiling water and weigh at hourly 

 intervals until the weight becomes constant. The use of clean, dry sand or asbestos 

 is admissible. 



ETHER EXTRACT. 



41 Indirect Method. — Official. 



Dissolve the dry butter, obtained in the moisture determination in which no 

 absorbent was used, in absolute ether or petroleum ether, transfer to a weighed 

 Gooch, with the aid of a wash bottle filled with the solvent and wash until free 

 from fat. Dry the Gooch and contents at the temperature of boiling water until 

 the weight is constant and determine the fat. 



42 Direct Method.— Official. 



From the dry butter, obtained in the determination of moisture, either with or 

 without the use of an absorbent, extract the fat with anhydrous, alcohol-free ether, 

 receiving the solution in a weighed flask. Evaporate the ether, dry the extract at 

 the temperature of boiling water and weigh at hourly intervals until the weight 

 is constant. 



43 CASEIN, ASH AND CHLORIN.— OFFICIAL. 



Cover the crucible, containing the residue from the fat determination by the 

 indirect method, 41, and heat gently at first, then raise the temperature gradually 

 to just below redness. The cover may then be removed and heating continued 

 until the contents of the crucible are white. The loss in weight represents casein, 

 and the residue in the crucible, mineral matter. Dissolve this mineral matter in 

 water slightly acidified with nitric acid and determine chlorin, either gravimetri- 

 cally as directed under I, 16 (a), or volumetrically as directed under III, 15. 



44 SALT.-OFFICIAL. 



Weigh in a counterpoised beaker 5-10 grams of butter, using portions of about 

 1 gram from different parts of the sample. Add about 20 cc. of hot water and, after 

 the butter is melted, transfer the whole to a separatory funnel. Insert the stopper 

 and shake for a few moments. Let stand until all the fat has collected on the top 

 of the water, then draw off the latter into a flask, being careful to let none of the 

 fat globules pass. Again add hot water, rinsing the beaker, and repeat the extrac- 

 tion 10-15 times, using 10-20 cc. of water each time. The washings will contain all 

 but a mere trace of the sodium chlorid originally present in the butter. Determine 

 the amount in the whole or an aliquot of the liquid by titration with standard silver 

 nitrate, using potassium chromate as an indicator. 



