38 DAIRY LABORATORY GUIDE 



EXERCISE 15 



DETERMINATION OF SALT IN DAIRY PRODUCTS 



Object: To determine the percentage of salt in dairy 

 products. 



Apparatus: Samples to be tested, torsion balance, 

 beaker, flask, burette, and N/10 silver nitrate solution. 



Preparation of Silver Nitrate Solution. In case no N/10 

 normal silver nitrate solution is at hand, obtain from the 

 drug store an ounce of chemically-pure silver nitrate crystals. 

 Weigh out 1.69 of the crystals and dissolve them in 100 c. c. of 

 distilled water or in pure soft water, when it is ready for use. 

 The silver nitrate is readily affected by sunlight; so it is best 

 kept in a glass-stoppered, preferably brown glass, bottle, so it 

 will not lose strength. 



Preparing Indicator. The indicator used is potassium 

 chromate. An ounce of chemically-pure chromate obtained 

 from the drug store and dissolved in 100 c. c. of distilled water 

 or pure soft water will make up a sufficient amount to 

 last indefinitely. 



Steps : 1. Weigh out 10 grams of butter in a beaker the 

 same as in the moisture determination. 



2. Melt the butter and transfer to a 250 c. c. stoppered 

 flask. Rinse the beaker with warm water several times and 

 transfer to the flask. 



3. Fill the flask to the 250 c. c. mark with warm water 

 and shake thoroughly until all of the salt is dissolved. Allow 

 the flask to stand quiet for a short time until the butter- 

 fat has collected on the surface and then remove it by means 

 of a pipette. 



4. Transfer 17.5 c. c. of the solution with a pipette to a 

 white cup; then add a drop of the potassium chromate 

 indicator. 



