124 METHODS OF ANALYSIS. 



2. Moisture. Official. 



Place 1.5 to 2.5 grams in a dish with a flat bottom having a surface of at 

 least 20 sq. cm. and dry at the temperature of boiling water until it ceases to 

 lose weight, each drying to be for only one hour. The use of clean dry sand or 

 asbestos is admissible and is necessary if a dish with a round bottom be 

 employed. 



3. Casein, Ash, and Chlorin. Official. 



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

 indirect method (see 4 (a)) and heat gently at first, gradually raising the tem- 

 perature to just below redness. The cover may then be removed and the. heat 

 continued until the contents of the crucible are white. The loss in weight rep- 

 resents casein, and the residue in the crucible, mineral matter. In this mineral 

 matter, dissolved in water slightly acidulated with nitric acid, determine chlorin, 

 either gravimetrically or volumetrically. 



4. Ether Extract, 

 (a) INDIRECT METHOD. OFFICIAL. 



Dissolve in the dish with absolute ether or petroleum ether the dry butter 

 obtained in the water determination in which no absorbent was used, transfer to 

 a weighed gooch with the aid of a wash bottle filled with the solvent and wash 

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

 boiling water until the weight is constant and calculate the fat 



(b) DIRECT METHOD. OFFICIAL. 



From the dry butter obtained in determining the water, 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 and dry the 

 extract at the temperature of boiling water until it ceases to lose weight, the 

 dryings not to exceed one hour each in duration. 



5. Salt. Official. 



Weigh in a counterpoised beaker from 5 to 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 the fat has all 

 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 to the beaker 

 and repeat the extraction from ten to fifteen times, using each time from 10 to 

 20 cc of water. The washings will contain all but a mere trace of the sodium 

 chlorid originally present in the butter. Determine its amount in the whole or 

 an aliquot of the liquid by the volumetric silver-nitrate method, with potassium 

 chromate as indicator. 



6. Examination of Fat. 



(a) PREPARATION OF SAMPLE. OFFICIAL. 



Melt the butter and keep it in a dry place at about 60 C. for two or three 

 hours, until the water and curd have entirely separated. Pour off the clear 

 supernatant fat and filter through a dry filter paper in a hot-water funnel con- 

 taining boiling water, or in an oven at about 60 C. Should the filtered liquid 

 fat not be perfectly clear it must be filtered again. 



