CKEAMERY PROBLEMS. 289 



71. To find acidity of cream when sweet milk or 

 water is used to reduce acidity. 



Problem: What will be the acidity of cream hav- 

 ing .65% acidity, when (a) 12% of water is added; 

 (b) when 12% of milk with an acidity of .15% is 

 added? 



Rule I. Divide the per cent of acidity in cream 

 to be diluted, by 100-f-the per cent of water to be 

 added. Multiply the quotient by 100, and the result 

 will be the per cent of acidity after diluting. 



Rule II. Multiply the per cent of milk to be ad- 

 ded by its acidity. To this add the acidity in per 

 cent in the cream to be diluted; divide the sum by 

 100+the per cent of milk to be added and multiply 

 the quotient by 100. The result is the acidity of the 

 diluted cream. 



Solution: (a) .65^(100+12)=.0058; .0058X100 

 — 58%. Ans. (b) .65+(12X.15)=.668; .668-^112= 

 .0059; .0059X100=.59%. Ans. 



Explanation: It will be seen that when we add 

 12% we add 12 lbs. to each 100 lbs. of cream. This 

 makes 112 lbs. of cream. "When the addition is 

 water, 112 lbs. of the cream contains .65% acid and 

 100 lbs. of the cream will test as many per cent as 

 112 is contained in .65%. This quotient multiplied 

 by 100 equals .58%. When we add milk which has 

 some acidity, we must first find out how much acid- 

 ity is added to the cream. This we find by multiply- 

 ing the amount added by its test. We add the test 

 of acidity of the cream and the acidity in the milk. 



