260 THE BOOK OF BUTTER 



The reading is calculated as follows: The molecular 

 weight of silver nitrate (AgNO 3 ) is 170 grams ; the molec- 

 ular weight of sodium chloride is 58.5 grams. Applying 

 the rule that the molecular weight of one substance is to 

 the molecular weight of another as the actual weight of 

 the first substance is to the actual weight of the second 

 when the molecules are chemically equal, the result is 

 as follows : 170 (molecular wt., AgNO 3 ) : 58.5 (molecular 

 wt., NaCl) : : .017 : X. There are .017 gram AgNO 3 in 

 1 c.c. of the N/10 solution. In the calculation, X is 

 equal to .00585 gram, which is the amount of salt that 

 1 c.c. of N/10 silver nitrate solution will neutralize. In 

 this determination, 10 grams of butter were put in 300 c.c. 

 of water. A Babcock pipetteful of this solution was ti- 

 trated. This pipette delivers 17.5 c.c. of liquid. Assuming 

 that in the titration 4 c.c. of N/10 silver nitrate was used 

 to neutralize the salt, then .00585 gram X 4 c.c. = .0234 

 gram of salt in one pipetteful of the solution. The quan- 

 tity of salt in the 300 c.c. solution is reckoned as follows : 

 300 -T- 17.5 c.c., the amount in one pipetteful, = 17.14 

 pipettefuls ; 17.14 X .0234 = .4 gram of salt in the 300 c.c. 

 of solution. This means that the 10 grams of butter 

 contained .4 gram of salt, .4 -f- 10 = .04 of a gram. This 

 .04 gram X 100 = 4.00 per cent salt. Thus it is seen 

 that when 10 grams of butter are melted in 300 c.c. of 

 water and a Babcock pipetteful is used for titration, the 

 final reading may be obtained without any calculation. 

 Each cubic centimeter of the N/10 silver nitrate used 

 is equal to 1 per cent salt. 



ACIDITY TEST OF MILK OR CREAM 



The acidity of milk products is formed largely by lactic 

 acid. This acidity is a fairly good criterion of measure of 



