646 TESTING BUTTER 



Additional Apparatus Required. "A 50-cubic centimeter bur- 

 ette graduated in tenth cubic centimeters. A 250-cubic centimeter 

 volumetric flask. A 25-cubic centimeter pipette. A 250-cubic cen- 

 timeter beaker or white cup. 



Chemicals Required. '"An aqueous silver-nitrate solution con- 

 taining 14.525 grams pure silver nitrate per liter. This solution 

 may be obtained from a chemical supply house. A 10 per cent 

 aqueous solution of potassium chromate, which may be obtained at 

 a drug store. 



Method. "To determine the percentage of salt the wash water, 

 obtained as previously directed in Paragraph IV, see Shaw test for 

 fat, is allowed to run into the 250-cubic centimeter flask, and the 

 operations in Paragraph IV conducted 3 times instead of but once, 

 the water each time being allowed to run into the flask. 



After the washings have become cool the flask is filled to the 

 mark with cold water and the contents mixed. Twenty-five cubic 

 centimeters, which represents 2 grams of the original sample, are 

 then measured with the pipette into the beaker or cup and titrated 

 with the silver-nitrate solution from the burette, using 2 or 3 drops 

 of the potassium-chromate solution as the indicator. The first 

 appearance of a permanent red is the end point. The silver-nitrate 

 solution is of such strength that 2 cubic centimeters represent 1 per 

 cent of salt if a 1-gram charge is used. In the above test where 



2 grams are represented ( FTX ^ the num ^er of cubic centimeters 



divided by 4 gives the percentage of salt in the original sample. As 

 an example, if the burette reading showed that 10.6 cubic centimeters 

 of the silver-nitrate solution were consumed in reaching the end 

 point, then 10.6 divided by 4, or 2.65, would be the percentage of 

 salt in that particular sample of butter. . 



The Perkins Salt Test. 



Professor A. E. Perkins of the Ohio Agricultural Experiment 

 Station recommends the following method for the determination of 

 the per cent of salt in butter : 



Weigh out either 5 or 10 grams of the butter to be tested, which 

 has previously been warmed to a salvy consistency and very thor- 

 oughly mixed, into any receptacle, such as a beaker or cup. Warm 

 gently until just melted, then add 20 or 30 cc. of commercial ace- 

 tone, and about 1 cc. of a saturated water solution of potassium chro- 



